1 00:00:00,506 --> 00:00:07,546 [ Silence ] 2 00:00:08,046 --> 00:00:08,346 >> All right. 3 00:00:08,756 --> 00:00:09,526 All right, we're back. 4 00:00:09,706 --> 00:00:11,126 This is Computer Science S76. 5 00:00:11,426 --> 00:00:13,686 So there weren't too many questions from you, 6 00:00:13,686 --> 00:00:15,786 so that means it's my turn to start asking questions. 7 00:00:15,786 --> 00:00:18,926 Last week we started talking about MVC, which, 8 00:00:18,966 --> 00:00:20,726 how about we'll start with the softball, stands for what? 9 00:00:20,726 --> 00:00:22,016 >> Model-view-controller. 10 00:00:22,076 --> 00:00:23,196 >> Model-view-controller. 11 00:00:23,196 --> 00:00:27,676 Okay. So what is the Controller in that acronym? 12 00:00:27,676 --> 00:00:27,946 >> [Inaudible response]. 13 00:00:27,946 --> 00:00:28,216 . 14 00:00:28,216 --> 00:00:30,556 >> Okay. Brains of the application, so it's the code 15 00:00:30,556 --> 00:00:32,576 that you write, the so-called business logic 16 00:00:32,576 --> 00:00:34,946 that governs the control of your application. 17 00:00:34,946 --> 00:00:37,966 It's the entry point to really the logic that you write. 18 00:00:37,966 --> 00:00:38,506 All right? 19 00:00:38,506 --> 00:00:40,586 How about the V, view? 20 00:00:40,586 --> 00:00:43,886 >> Interactions with the user. 21 00:00:44,006 --> 00:00:45,526 >> Yeah, so interactions with the user. 22 00:00:45,526 --> 00:00:47,756 So view typically deals with presentation, 23 00:00:47,756 --> 00:00:49,946 both the anesthetics thereof, 24 00:00:49,946 --> 00:00:52,226 so how you're displaying information to the user, 25 00:00:52,386 --> 00:00:54,896 and then it typically has some UI mechanisms, like buttons 26 00:00:54,896 --> 00:00:58,366 and text fields and whatnot, that somehow send messages back 27 00:00:58,366 --> 00:00:59,926 to which of the letters? 28 00:01:00,536 --> 00:01:01,666 >> The Controller. 29 00:01:01,666 --> 00:01:02,366 >> The Controller. 30 00:01:02,366 --> 00:01:05,876 So you have this bidirectional arrow essentially between your C 31 00:01:05,876 --> 00:01:07,506 and your V, so the two are talking, 32 00:01:07,506 --> 00:01:11,996 but you do not have an arrow between, say, V and M directly. 33 00:01:11,996 --> 00:01:14,886 Rather the model is where you typically represent your data, 34 00:01:14,886 --> 00:01:17,236 and we'll do a simple example tonight of what you might want 35 00:01:17,236 --> 00:01:20,286 to model with its own class that we write ourselves. 36 00:01:20,676 --> 00:01:23,146 But typically, all of those communications should be 37 00:01:23,206 --> 00:01:25,846 marshaled through the so-called Controller, 38 00:01:25,846 --> 00:01:27,946 so that's where really the intellectual property 39 00:01:27,946 --> 00:01:30,376 of your app tends to be, in the aesthetics or in the View. 40 00:01:30,376 --> 00:01:33,626 And then the model is where we'll do our data typing 41 00:01:33,626 --> 00:01:35,606 and our data representation encapsulation. 42 00:01:35,606 --> 00:01:36,776 We'll do a bit of that in just a bit. 43 00:01:36,776 --> 00:01:37,566 All right. 44 00:01:37,596 --> 00:01:41,056 So that was MVC, and in what -- 45 00:01:41,056 --> 00:01:43,256 what form does this take in the world of iOS? 46 00:01:43,476 --> 00:01:47,616 Well, in iOS, we have a few classes with the UI kit, 47 00:01:47,666 --> 00:01:51,376 so this is the API that provides access 48 00:01:51,376 --> 00:01:53,256 to UI related things in iOS. 49 00:01:53,256 --> 00:01:56,236 And UIApplication was a class that we barely spent any time 50 00:01:56,236 --> 00:01:59,856 with because we just make reference to it in Main, 51 00:01:59,996 --> 00:02:02,566 essentially, where we have a new UIApplication, 52 00:02:02,566 --> 00:02:03,236 and that's the class 53 00:02:03,236 --> 00:02:05,076 that embodies your actual application. 54 00:02:05,076 --> 00:02:07,396 But beyond that, we don't really need to care too much about it, 55 00:02:07,766 --> 00:02:10,156 but UIApplicationDelegate is a class 56 00:02:10,556 --> 00:02:13,186 that we spent a little more time talking about, 57 00:02:13,946 --> 00:02:21,046 and what is that class's role when you create an iOS app? 58 00:02:21,376 --> 00:02:24,006 Use it in a sentence that makes it sound 59 00:02:24,006 --> 00:02:26,206 like technically you're comfy with what its role is. 60 00:02:27,096 --> 00:02:28,226 >> Isn't that where you put your code? 61 00:02:28,596 --> 00:02:29,566 >> So it's where you put your code, 62 00:02:29,566 --> 00:02:30,806 or at least the first entry point. 63 00:02:30,806 --> 00:02:32,816 You wouldn't put your code in Main.M, 64 00:02:32,816 --> 00:02:35,606 but rather you might first put it in UIApplicationDelegate, 65 00:02:35,786 --> 00:02:38,526 and conceptually it's to this class, or an object thereof, 66 00:02:38,816 --> 00:02:41,476 that controlled your application is delegated or passed. 67 00:02:41,726 --> 00:02:43,336 So he's now the guy in charge. 68 00:02:43,596 --> 00:02:46,166 But as soon as we started doing more interesting applications 69 00:02:46,166 --> 00:02:47,816 than just rectangles on the screen 70 00:02:47,816 --> 00:02:49,536 and started getting interactions from users, 71 00:02:49,786 --> 00:02:53,166 we further delegated control from the UIApplicationDelegate 72 00:02:53,406 --> 00:02:55,286 to an object of what type? 73 00:02:57,056 --> 00:02:57,636 >> UIViewController. 74 00:02:57,636 --> 00:02:58,316 >> UIViewController. 75 00:02:58,316 --> 00:02:59,936 And we don't have to, per se. 76 00:02:59,936 --> 00:03:02,216 Games don't necessarily use that same class, 77 00:03:02,216 --> 00:03:04,446 and custom applications don't necessarily use that class, 78 00:03:04,446 --> 00:03:06,836 but the UIViewController's nice because it comes 79 00:03:06,836 --> 00:03:08,796 with a whole bunch of built in functionality 80 00:03:09,046 --> 00:03:11,776 for handling various common paradigms, like buttons 81 00:03:11,776 --> 00:03:14,106 and sliding and tabular views and so forth. 82 00:03:14,106 --> 00:03:16,286 So it's a common starting point, certainly for the types 83 00:03:16,286 --> 00:03:18,486 of menued applications we've looked at thus far. 84 00:03:18,756 --> 00:03:22,416 And the UIViewController in turn makes you solve bunches 85 00:03:22,416 --> 00:03:25,966 of UIView objects, but typically not just generic UIView objects, 86 00:03:25,966 --> 00:03:28,366 but typically not just generic UIView objects. 87 00:03:28,366 --> 00:03:34,486 What are some subclasses that we've used and talked about? 88 00:03:34,486 --> 00:03:40,476 Two of which I've enumerated tonight, albeit off camera. 89 00:03:40,566 --> 00:03:43,646 Starts with UI, ends with utton. 90 00:03:44,366 --> 00:03:45,546 >> UI Buttons. 91 00:03:45,646 --> 00:03:46,906 >> Okay, so UI Buttons [laughter]. 92 00:03:46,906 --> 00:03:48,096 So this was just a subclass, 93 00:03:48,456 --> 00:03:50,306 and thus far we've essentially used these things 94 00:03:50,306 --> 00:03:51,746 by dragging and dropping. 95 00:03:51,746 --> 00:03:53,976 But we did have a quick glimpse last time 96 00:03:54,296 --> 00:03:59,176 at no Nib.Xcode project, which was a reimplementation 97 00:03:59,176 --> 00:04:01,756 of that super simple app that gave me a text field 98 00:04:01,756 --> 00:04:04,186 for my name, gave me a button with -- 99 00:04:04,186 --> 00:04:07,796 to click on to actually then trigger a UIAlertView saying 100 00:04:07,796 --> 00:04:09,766 hello David, or hello such and such. 101 00:04:09,976 --> 00:04:11,636 And we dragged and dropped that UI Button, 102 00:04:11,636 --> 00:04:15,216 but UI Button is just a specific incarnation of UIView, 103 00:04:15,396 --> 00:04:17,796 and if you think back to Xcode and think back 104 00:04:17,796 --> 00:04:20,086 to Interface Builder, that drag and drop interface, 105 00:04:20,086 --> 00:04:21,916 what we're essentially doing by dragging 106 00:04:21,916 --> 00:04:24,766 and dropping is dropping these little objects on top 107 00:04:24,766 --> 00:04:27,336 of a canvas, and they can overlay, overlay, overlay. 108 00:04:27,336 --> 00:04:28,626 And we'll do a little more of that 109 00:04:28,626 --> 00:04:31,076 in a different sense tonight by actually responding 110 00:04:31,076 --> 00:04:34,396 to arbitrary key presses, or pinches, for zooms and the like, 111 00:04:34,396 --> 00:04:36,476 so we can actually listen to the entire U View -- 112 00:04:36,636 --> 00:04:38,256 UIView, as we will see. 113 00:04:38,486 --> 00:04:41,316 UIWindow finally was a special case of a UIView. 114 00:04:41,316 --> 00:04:43,276 It has some additional stuff baked into it 115 00:04:43,466 --> 00:04:45,856 that essentially describes the full rectangular area 116 00:04:46,166 --> 00:04:48,106 of the iOS device in question. 117 00:04:48,106 --> 00:04:50,486 But today we'll spend a bit more time in UIViewController 118 00:04:50,656 --> 00:04:54,556 and UIView, but we'll see those other classes again along 119 00:04:54,556 --> 00:04:54,946 the way. 120 00:04:55,086 --> 00:04:56,786 So let's see. 121 00:04:56,786 --> 00:04:59,336 So last time, we looked at a whole bunch of these templates. 122 00:04:59,336 --> 00:05:01,106 None of these templates are strictly necessary. 123 00:05:01,106 --> 00:05:03,516 You could just start with nothing in your project 124 00:05:03,516 --> 00:05:04,936 and start writing files by hand. 125 00:05:05,226 --> 00:05:07,296 The problem is you just end up reinventing the wheel. 126 00:05:07,296 --> 00:05:10,126 There's a lot of configuration details that we saw in the form 127 00:05:10,126 --> 00:05:11,946 of Property Lists, those key value pairs 128 00:05:11,946 --> 00:05:13,646 that would just be a pain to do manually. 129 00:05:13,646 --> 00:05:15,626 So Xcode helps jumpstart things either 130 00:05:15,626 --> 00:05:16,706 with an empty application, 131 00:05:16,706 --> 00:05:18,756 which has the bare minimum of configuration. 132 00:05:18,946 --> 00:05:21,926 And then we looked at Single View last time and then a lot 133 00:05:21,926 --> 00:05:24,266 of you looked at Utility View and you're knee-deep 134 00:05:24,266 --> 00:05:26,886 in a Utility View application for Evil Hangman. 135 00:05:27,246 --> 00:05:30,586 So if we proceed a little further today, let's take a look 136 00:05:30,766 --> 00:05:33,546 at these two last ones, not because they in 137 00:05:33,546 --> 00:05:35,696 and of themselves are applications you'll need to use 138 00:05:35,696 --> 00:05:37,836 for the project, but rather because they're illustrative 139 00:05:38,006 --> 00:05:40,206 of somewhat more complex applications 140 00:05:40,206 --> 00:05:43,656 that you might implement that nonetheless assume familiarity 141 00:05:43,906 --> 00:05:46,766 with the overall structure we had earlier. 142 00:05:46,766 --> 00:05:47,476 So let's do this. 143 00:05:47,476 --> 00:05:49,556 First, let's start somewhere simple. 144 00:05:49,556 --> 00:05:52,346 I'm going to go into Xcode, and I'm going to first start, 145 00:05:52,346 --> 00:05:55,296 not with an empty application, which was super uninteresting 146 00:05:55,706 --> 00:05:57,826 by the end of last week, but Single View Application, 147 00:05:57,826 --> 00:05:59,366 and then we'll quickly build on from there. 148 00:05:59,366 --> 00:06:02,496 I'm going to go ahead and call this Single View. 149 00:06:02,496 --> 00:06:04,526 I'm going to just store it on my desktop. 150 00:06:04,526 --> 00:06:07,366 I'm going to uncheck Storyboards here, click next, 151 00:06:07,366 --> 00:06:09,376 and then I'm going to go ahead and click okay. 152 00:06:09,376 --> 00:06:13,076 And now we have the following boilerplate files. 153 00:06:13,296 --> 00:06:16,506 So suppose by contrast I didn't just create this right in front 154 00:06:16,506 --> 00:06:18,646 of you, but you were handed this project from someone else, 155 00:06:18,646 --> 00:06:19,586 and you want to wrap your mind 156 00:06:19,586 --> 00:06:21,056 as to what's going on inside of it. 157 00:06:21,176 --> 00:06:22,386 Where's the best place to start 158 00:06:22,386 --> 00:06:24,356 to understand what you've been handed? 159 00:06:25,336 --> 00:06:26,586 >> A .H file. 160 00:06:26,806 --> 00:06:27,796 ViewController.H. 161 00:06:28,046 --> 00:06:31,176 >> Okay. ViewController.H. I would propose that's maybe a 162 00:06:31,176 --> 00:06:33,626 little too deep at first glance. 163 00:06:33,626 --> 00:06:35,996 Why don't we start where the beginning of the story begins? 164 00:06:36,416 --> 00:06:36,816 >> AppDelegate [inaudible]? 165 00:06:37,316 --> 00:06:40,056 >> Yeah, AppDelegate, and really if we want to be super anal 166 00:06:40,056 --> 00:06:42,276 about this, technically it's Main.M 167 00:06:42,276 --> 00:06:43,706 that kick starts the whole process, 168 00:06:43,826 --> 00:06:45,906 and a quick glance should at least reassure 169 00:06:45,906 --> 00:06:48,066 that there's nothing special, nothing different there. 170 00:06:48,176 --> 00:06:50,576 But indeed it's in this file that we see mention, 171 00:06:50,576 --> 00:06:53,506 not only of UIApplication, but also AppDelegate, 172 00:06:53,506 --> 00:06:55,116 to whom we're going to delegate control. 173 00:06:55,116 --> 00:06:57,266 So we've confirmed that there's nothing distinct in there. 174 00:06:57,586 --> 00:06:59,946 So now I would propose among the AppDelegate files, 175 00:07:00,326 --> 00:07:02,316 starting with the .H is probably the better place, 176 00:07:02,316 --> 00:07:04,316 because it gives you, in theory, an overview of what's 177 00:07:04,316 --> 00:07:07,686 about to go on, and it also gives you a sense of what needs 178 00:07:07,686 --> 00:07:09,566 to be implemented in the .M file. 179 00:07:10,066 --> 00:07:11,056 So what's going on here? 180 00:07:11,056 --> 00:07:11,916 Well, a quick recap. 181 00:07:11,916 --> 00:07:13,256 The import line does what for us? 182 00:07:13,956 --> 00:07:20,106 >> It imports the user interface kit. 183 00:07:20,256 --> 00:07:20,696 >> Okay, good. 184 00:07:20,696 --> 00:07:22,456 It imports the user interface kit. 185 00:07:22,726 --> 00:07:23,616 And what does that mean? 186 00:07:23,616 --> 00:07:25,836 So in that .H file, there's a whole bunch 187 00:07:25,836 --> 00:07:28,196 of class declarations, perhaps, maybe a bunch 188 00:07:28,196 --> 00:07:29,596 of constants that are defined. 189 00:07:29,706 --> 00:07:31,986 A whole bunch of things that we want to take for granted exist, 190 00:07:31,986 --> 00:07:34,596 and this is our way of teaching Xcode that we want 191 00:07:34,596 --> 00:07:35,966 to use the code that someone else wrote. 192 00:07:35,966 --> 00:07:39,176 All right, on the next line we have at Class ViewController. 193 00:07:39,696 --> 00:07:41,876 Actually, that's a little strange. 194 00:07:42,116 --> 00:07:46,476 There's a semicolon, yet no implementation of the class. 195 00:07:47,786 --> 00:07:50,906 What is it with this line here, at Class ViewController, 196 00:07:50,906 --> 00:07:52,906 which we've not really spent time on? 197 00:07:53,126 --> 00:07:53,486 Yeah. 198 00:07:54,146 --> 00:08:04,466 >> So the at Class actually tells it that it's [inaudible], 199 00:08:04,466 --> 00:08:06,716 but doesn't actually import it. 200 00:08:06,716 --> 00:08:07,186 >> Exactly. 201 00:08:07,426 --> 00:08:10,316 >> Unless you were going to use one of its methods, 202 00:08:10,316 --> 00:08:13,546 that should suffice to tell it that it exists. 203 00:08:13,546 --> 00:08:14,106 >> Exactly. 204 00:08:14,106 --> 00:08:16,536 So we didn't spend time on this last time, 205 00:08:16,536 --> 00:08:20,196 but this is what's called a forward declaration. 206 00:08:20,196 --> 00:08:24,806 It's a little hint to the compiler saying there is going 207 00:08:24,806 --> 00:08:27,686 to be a class called ViewController. 208 00:08:27,686 --> 00:08:30,686 I'm not going to tell you anything more about it, 209 00:08:30,686 --> 00:08:33,096 but if you see mentions of ViewController elsewhere 210 00:08:33,276 --> 00:08:34,836 in this file, don't complain. 211 00:08:34,836 --> 00:08:37,386 Don't give me any red warning saying that's no -- 212 00:08:37,386 --> 00:08:38,476 that not allowed. 213 00:08:38,476 --> 00:08:41,606 This is just teaching the compiler what's actually going 214 00:08:41,786 --> 00:08:43,686 to come, and indeed where are we using that? 215 00:08:43,686 --> 00:08:46,236 Well, a few lines later we're declaring a property whose 216 00:08:46,236 --> 00:08:48,666 purpose in life is to store a pointer 217 00:08:48,666 --> 00:08:51,056 to a ViewController object. 218 00:08:51,056 --> 00:08:53,216 So this is, long story short, 219 00:08:53,216 --> 00:08:56,566 in way of avoiding potential circular references whereby one 220 00:08:56,566 --> 00:09:00,536 file might import another, might import another. 221 00:09:00,536 --> 00:09:06,836 A common paradigm is if you only need to make mention 222 00:09:07,116 --> 00:09:09,196 of the class in this way in your .H file, 223 00:09:09,676 --> 00:09:13,276 just to use a forward declaration and not 224 00:09:13,276 --> 00:09:15,926 to import the whole ViewController.H file, 225 00:09:15,926 --> 00:09:16,866 for instance. 226 00:09:16,866 --> 00:09:21,036 Okay, what's this third, more interesting line saying? 227 00:09:21,956 --> 00:09:25,696 At Interface AppDelegate colon UIResponder angled 228 00:09:25,696 --> 00:09:27,596 brackets UIApplicationDelegate. 229 00:09:27,596 --> 00:09:28,656 Let's start easily. 230 00:09:28,656 --> 00:09:29,416 This just declares what? 231 00:09:29,416 --> 00:09:31,426 What's this mention in black of AppDelegate? 232 00:09:31,426 --> 00:09:32,096 >> Name of the class. 233 00:09:32,096 --> 00:09:33,346 >> Name of the class, all right? 234 00:09:33,346 --> 00:09:35,006 The colon UIResponder means? 235 00:09:35,006 --> 00:09:35,073 >> [Inaudible audience response]. 236 00:09:35,073 --> 00:09:36,706 >> It's the -- UIResponder is the parent of the class, 237 00:09:36,706 --> 00:09:38,906 so AppDelegate is going to descend 238 00:09:38,906 --> 00:09:41,076 from UIResponder, and someone else? 239 00:09:41,106 --> 00:09:42,336 The UIApplicationDelegate in angled brackets? 240 00:09:42,366 --> 00:09:42,786 >> It's a protocol. 241 00:09:42,816 --> 00:09:43,986 >> It's a protocol, so we're saying that we're going 242 00:09:44,016 --> 00:09:45,366 to implement the UIApplicationDelegate protocol, 243 00:09:45,396 --> 00:09:46,566 and this makes sense because the class, after all, 244 00:09:46,596 --> 00:09:47,136 is called AppDelegate. 245 00:09:47,166 --> 00:09:47,346 All right? 246 00:09:47,376 --> 00:09:48,006 What are the two properties? 247 00:09:48,036 --> 00:09:48,786 Well, we saw one ViewController. 248 00:09:48,816 --> 00:09:50,376 We have another pointer to the UIWindow that'll give us access 249 00:09:50,406 --> 00:09:51,966 to the full rectangular portion of the screen, and that's it. 250 00:09:51,996 --> 00:09:52,176 All right? 251 00:09:52,206 --> 00:09:53,076 So now let's dive into the M file. 252 00:09:53,106 --> 00:09:53,736 All of that is boilerplate. 253 00:09:53,766 --> 00:09:55,116 None of that is different from what we saw last week. 254 00:09:55,146 --> 00:09:56,556 This file's always a little overwhelming at first glance 255 00:09:56,586 --> 00:09:57,426 when you have all of these comments, 256 00:09:57,456 --> 00:09:58,716 but that just means they're not really doing anything. 257 00:09:58,746 --> 00:10:00,246 So let's ignore anything that's not actually doing anything 258 00:10:00,276 --> 00:10:01,896 functional, and focus only on this first method up top named, 259 00:10:01,926 --> 00:10:02,976 what's the name of this method that remains? 260 00:10:05,916 --> 00:10:06,236 >> AppDelegate? 261 00:10:06,236 --> 00:10:10,436 >> Not AppDelegate, so that's the -- that's the class name. 262 00:10:10,526 --> 00:10:11,646 The name of the method is? 263 00:10:11,986 --> 00:10:13,626 >> didFinishLaunchingWithOptions. 264 00:10:13,676 --> 00:10:16,276 >> Yeah, application didFinishLaunchingWithOptions, 265 00:10:16,276 --> 00:10:19,576 so longly named method there, but what's this doing? 266 00:10:19,576 --> 00:10:21,396 So first, it's allocating a window. 267 00:10:21,636 --> 00:10:23,906 It's initializing it with a frame that's just referring 268 00:10:23,906 --> 00:10:26,326 to the rectangle, if we keep describing it. 269 00:10:26,326 --> 00:10:28,996 ViewController gets -- so here is 270 00:10:28,996 --> 00:10:32,406 where we're effectively configuring our AppDelegate 271 00:10:32,536 --> 00:10:34,076 with another guy to whom we're going 272 00:10:34,076 --> 00:10:36,106 to delegate control, the ViewController. 273 00:10:36,336 --> 00:10:39,706 Self.ViewController is a property that's built 274 00:10:39,706 --> 00:10:41,836 into the AppDelegate class, so if you actually look 275 00:10:41,836 --> 00:10:45,356 up the documentation for a UIApplicationDelegate, 276 00:10:45,356 --> 00:10:47,756 you'll see that it comes with that property, 277 00:10:47,756 --> 00:10:49,176 so we're setting it in that way. 278 00:10:49,456 --> 00:10:51,016 Finally we're setting the -- sorry. 279 00:10:51,426 --> 00:10:54,006 This is our property that we declared in the .H file, 280 00:10:54,066 --> 00:10:56,726 but it comes with a RootViewController property 281 00:10:56,726 --> 00:10:59,386 in the window, that's in the UIWindow documentation. 282 00:10:59,666 --> 00:11:02,296 And then that second to last line, Make Key Invisible, 283 00:11:02,556 --> 00:11:04,466 just gives control 284 00:11:04,566 --> 00:11:07,286 to the ViewIController to the foreground. 285 00:11:07,996 --> 00:11:09,396 What else does this application do? 286 00:11:09,396 --> 00:11:13,386 Anything? So that's it. 287 00:11:13,386 --> 00:11:15,146 All we have is the Nib where we could start 288 00:11:15,146 --> 00:11:17,026 to put our user interface, but beyond that, 289 00:11:17,276 --> 00:11:20,236 this application does terribly, terribly little. 290 00:11:21,026 --> 00:11:24,856 So let's try to see -- first, any questions? 291 00:11:24,856 --> 00:11:28,706 So let's take a more complex tour and see 292 00:11:28,706 --> 00:11:33,216 if we can't now understand a new application entirely, 293 00:11:33,436 --> 00:11:39,496 but this time while thinking about it in the context 294 00:11:39,496 --> 00:11:41,096 of applications we've seen thus far. 295 00:11:41,096 --> 00:11:43,746 So among tonight's source code is a folder called 296 00:11:43,746 --> 00:11:44,756 Master Detail. 297 00:11:44,986 --> 00:11:48,246 This is essentially a simplified version of the standard template 298 00:11:48,246 --> 00:11:50,796 that comes with Xcode, so all I did was tidy things up 299 00:11:50,796 --> 00:11:52,506 and remove things that didn't need to be there. 300 00:11:52,686 --> 00:11:55,406 As usual, let's go into our Main.M file. 301 00:11:55,406 --> 00:11:57,906 Let me close some superfluous windows over there. 302 00:11:58,126 --> 00:11:59,216 Nothing new happening here, 303 00:11:59,266 --> 00:12:00,996 so that's the same file we saw earlier. 304 00:12:01,156 --> 00:12:02,326 What file should we probably dive 305 00:12:02,326 --> 00:12:04,406 into next following the same rule of thumb? 306 00:12:04,736 --> 00:12:05,036 >> AppDelegate. 307 00:12:05,416 --> 00:12:06,596 >> Okay, so AppDelegate. 308 00:12:06,596 --> 00:12:09,866 Start with the .H. That looks perfectly the same, 309 00:12:09,866 --> 00:12:10,816 so nothing new there. 310 00:12:11,136 --> 00:12:16,836 AppDelegate.M, so here we have what seems to be the same code 311 00:12:16,836 --> 00:12:21,476 as before, except for -- any differences? 312 00:12:21,626 --> 00:12:22,156 >> MasterViewController. 313 00:12:22,856 --> 00:12:25,496 >> So we're instantiating a MasterViewController. 314 00:12:25,496 --> 00:12:26,336 So that's interesting. 315 00:12:26,336 --> 00:12:29,276 It's not just a ViewController, it's a MasterViewController, 316 00:12:29,496 --> 00:12:34,246 and we're making it the RootViewController, so to speak. 317 00:12:34,246 --> 00:12:35,436 So most of this code is the same, 318 00:12:35,436 --> 00:12:37,136 but I'm instantiating a different class name, 319 00:12:37,396 --> 00:12:39,926 but that's because someone at Apple decided for this template 320 00:12:39,926 --> 00:12:42,796 that we're not going to have one ViewController implemented 321 00:12:42,796 --> 00:12:45,286 for you in .H and .M. We're going to have what appears 322 00:12:45,286 --> 00:12:48,276 to be two: Master ViewController and Detail ViewController. 323 00:12:48,476 --> 00:12:49,676 So at this point I'm a little puzzled 324 00:12:49,676 --> 00:12:51,626 as to what this thing's going to do, so let me go ahead 325 00:12:51,626 --> 00:12:52,866 and just run the application, 326 00:12:53,076 --> 00:12:54,816 and see if we can't then work backwards 327 00:12:54,816 --> 00:12:58,156 as to how the behavior we're about to see is functioning. 328 00:12:58,156 --> 00:13:00,076 So let me go ahead and foreground the simulator, 329 00:13:00,356 --> 00:13:03,206 and in just a moment, we'll see it pop to the foreground. 330 00:13:03,866 --> 00:13:06,176 Lately the simulator has been loading a little slowly, 331 00:13:06,176 --> 00:13:06,966 but there we have it. 332 00:13:07,686 --> 00:13:10,526 And now we have, interesting, an application 333 00:13:10,736 --> 00:13:12,526 that has nothing going on here. 334 00:13:12,726 --> 00:13:15,486 You can just about see the horizontal lines, 335 00:13:15,486 --> 00:13:17,726 so this is some kind of tabular view going on, 336 00:13:17,956 --> 00:13:20,646 and this application, the starting point, is designed just 337 00:13:20,646 --> 00:13:22,006 to do something stupid, just 338 00:13:22,006 --> 00:13:25,336 to insert a new row every time you click the plus. 339 00:13:25,516 --> 00:13:29,306 And it's choosing the timestamp in UTC, so universal -- 340 00:13:29,916 --> 00:13:33,566 universal time, and adding a row accordingly. 341 00:13:33,636 --> 00:13:35,856 So if I do that ad nauseum, we'll just get lots of lots 342 00:13:35,856 --> 00:13:38,576 of rows, but you might recall this paradigm in iOS. 343 00:13:38,576 --> 00:13:40,496 If I click edit, I get this familiar UI. 344 00:13:40,496 --> 00:13:42,666 I can go ahead and delete, say, that one, 345 00:13:42,666 --> 00:13:45,646 by clicking that circle, then clicking the delete button. 346 00:13:45,916 --> 00:13:49,516 Then I say done, and so there we have that functionality. 347 00:13:49,516 --> 00:13:52,806 And if I click a row itself, Detail View Content Goes Here. 348 00:13:53,076 --> 00:13:54,986 So what's just happened apparently is 349 00:13:54,986 --> 00:13:56,386 that we've made some kind of transition 350 00:13:56,656 --> 00:13:58,186 from the Master ViewController 351 00:13:58,416 --> 00:14:00,546 to what they call the Detail ViewController, 352 00:14:00,546 --> 00:14:03,486 so this is illustrative now of how you can hand off control 353 00:14:03,486 --> 00:14:04,916 between two ViewControllers. 354 00:14:05,126 --> 00:14:06,966 Recall that you've essentially been doing this 355 00:14:06,966 --> 00:14:09,406 in the utility application, or you will soon be doing this 356 00:14:09,406 --> 00:14:11,926 in the utility application for Evil Hangman, 357 00:14:12,186 --> 00:14:13,396 but you were choosing a different type 358 00:14:13,786 --> 00:14:15,506 of transition Rather than side to side, 359 00:14:15,506 --> 00:14:17,336 you were doing front to back flipping. 360 00:14:17,666 --> 00:14:21,396 So this one still is a little different in its implementation. 361 00:14:21,396 --> 00:14:24,126 Let's next go into, from AppDelegate.M, 362 00:14:24,126 --> 00:14:27,326 let's start with Master ViewController.H. Is there 363 00:14:27,326 --> 00:14:29,036 anything of interest in here? 364 00:14:29,266 --> 00:14:32,256 So Master ViewController has a property that's going 365 00:14:32,256 --> 00:14:33,946 to store the address of what kind of object? 366 00:14:33,946 --> 00:14:40,556 Looks like a Detail ViewController.. 367 00:14:40,746 --> 00:14:42,326 So if you think about this high level, 368 00:14:42,546 --> 00:14:45,356 the RootViewController's the Master ViewController. 369 00:14:45,616 --> 00:14:47,516 He apparently is somehow going to have attached 370 00:14:47,736 --> 00:14:50,466 to him the address of a Detail ViewController, 371 00:14:50,586 --> 00:14:51,926 so it seems to be the case, indeed, 372 00:14:51,926 --> 00:14:53,796 that the Master ViewController is in charge. 373 00:14:54,016 --> 00:14:55,736 Now we haven't done any of that wiring yet, 374 00:14:55,736 --> 00:14:58,536 so let's go into the .M file for Master ViewController, 375 00:14:58,816 --> 00:15:01,166 get the lay of the land, this is a little overwhelming 376 00:15:01,166 --> 00:15:01,866 but we'll get there. 377 00:15:02,186 --> 00:15:04,716 So now let me scroll back up to the top 378 00:15:04,936 --> 00:15:06,846 and see what's interesting here. 379 00:15:06,846 --> 00:15:10,666 So let's focus first on one of these at a time. 380 00:15:10,666 --> 00:15:13,756 So here's a method called In It With Nib Name. 381 00:15:14,006 --> 00:15:16,766 This has typically been called automatically for us, 382 00:15:16,766 --> 00:15:18,626 because we've had a bunch of starting points 383 00:15:18,806 --> 00:15:20,356 in our applications thus far in class 384 00:15:20,796 --> 00:15:22,456 where we had those .XID files. 385 00:15:22,656 --> 00:15:26,536 Somehow they were wired up to my code and loaded automatically, 386 00:15:26,716 --> 00:15:29,706 and we just initialized them based on the XML file 387 00:15:29,706 --> 00:15:32,336 that is the .XID file somewhere on my hard drive. 388 00:15:32,686 --> 00:15:35,496 But now we're explicitly implementing in In It 389 00:15:35,496 --> 00:15:40,286 With Nib Name bundle method, and if I hover over this thing 390 00:15:40,286 --> 00:15:41,796 and check the question mark, 391 00:15:41,966 --> 00:15:44,676 notice that there's a whole bunch of documentation in here 392 00:15:44,946 --> 00:15:46,936 and this method appears to come 393 00:15:46,936 --> 00:15:52,846 from an ancestor class known as UIViewController. 394 00:15:53,246 --> 00:15:54,926 So if we really look underneath the hood, 395 00:15:54,926 --> 00:15:57,766 Master ViewController descends from a new class 396 00:15:58,076 --> 00:16:01,296 that gives us the tabular View, UITableViewController, 397 00:16:01,446 --> 00:16:03,526 which in turn descends from the thing we've seen 398 00:16:03,526 --> 00:16:05,946 in applications thus far, UIViewController. 399 00:16:06,186 --> 00:16:07,976 So long story short, if I actually start 400 00:16:07,976 --> 00:16:11,336 to read this documentation, this will explain how the In It 401 00:16:11,336 --> 00:16:13,466 With Nib Name bundle method works, 402 00:16:13,586 --> 00:16:15,876 and it is the guy that's responsible for loading 403 00:16:15,876 --> 00:16:19,356 from the hard drive that .XID file, and somehow making all 404 00:16:19,356 --> 00:16:21,826 of the connections we discussed last weekend in lab. 405 00:16:22,226 --> 00:16:24,516 So it's doing one additional thing though. 406 00:16:24,926 --> 00:16:28,686 It's calling first the superclasses implementation 407 00:16:28,686 --> 00:16:31,976 of that same method, In It With Nib Name bundle. 408 00:16:33,096 --> 00:16:34,856 So that's been called automatically for us, 409 00:16:34,856 --> 00:16:37,186 because we have not explicitly implemented this method thus 410 00:16:37,186 --> 00:16:40,396 far, but it's also doing what, in high-level terms apparently? 411 00:16:41,006 --> 00:16:44,526 What does it appear to be doing? 412 00:16:45,076 --> 00:16:48,536 You seem to have a guess in mind. 413 00:16:48,996 --> 00:16:50,446 Oh yes, yeah. 414 00:16:50,666 --> 00:16:54,056 >> [Inaudible] initializes the [inaudible] class. 415 00:16:54,236 --> 00:16:56,326 >> Initializes the -- oh, the first line does, yes. 416 00:16:56,366 --> 00:16:57,716 Sorry. Let me change my highlighting. 417 00:16:58,006 --> 00:17:00,476 So it's not commented, but was it -- 418 00:17:00,476 --> 00:17:02,036 what do these three lines seem to be doing? 419 00:17:02,146 --> 00:17:06,266 >> Setting the title. 420 00:17:06,466 --> 00:17:10,306 >> Yeah, setting the title of self, so self.title. 421 00:17:10,306 --> 00:17:10,966 What is self? 422 00:17:10,966 --> 00:17:13,226 What type of object is self at this point in time? 423 00:17:13,226 --> 00:17:14,076 >> Master ViewController. 424 00:17:14,506 --> 00:17:15,706 >> So it's a Master ViewController, 425 00:17:15,706 --> 00:17:18,006 which in turn is a UITableViewController, 426 00:17:18,006 --> 00:17:19,756 which in turn is a UIViewController, 427 00:17:19,916 --> 00:17:21,766 so if we really started poking around the docs, 428 00:17:21,766 --> 00:17:22,656 we would probably see 429 00:17:22,656 --> 00:17:24,646 that UIViewController's have a property called? 430 00:17:24,646 --> 00:17:24,816 >> Title. 431 00:17:26,046 --> 00:17:28,376 >> Title. And indeed, that's where this is coming from, 432 00:17:28,376 --> 00:17:29,826 our UITableViewControllers. 433 00:17:29,826 --> 00:17:32,376 And if we go back to the application that was running, 434 00:17:32,606 --> 00:17:34,756 notice when we're here, it's the title master, 435 00:17:35,016 --> 00:17:36,096 that's where they came from. 436 00:17:36,096 --> 00:17:38,256 So we could have typed this in manually into the Nib, 437 00:17:38,256 --> 00:17:40,256 but because we created the ViewController N code, 438 00:17:40,566 --> 00:17:42,226 we don't actually have to do that there. 439 00:17:42,466 --> 00:17:44,716 Alright so this, as an aside, is a common paradigm. 440 00:17:44,716 --> 00:17:48,746 Anytime you modify self, it's common to call 441 00:17:48,746 --> 00:17:51,856 to check is self -- if self is non-null, 442 00:17:51,856 --> 00:17:53,716 so that is if everything went okay 443 00:17:53,716 --> 00:17:56,046 and the previous line did not return nil, 444 00:17:56,116 --> 00:17:58,146 meaning there's some memory error or the like, 445 00:17:58,446 --> 00:18:01,656 you check first that self exists okay before touching one 446 00:18:01,656 --> 00:18:03,676 of its properties as we did here with self.title. 447 00:18:03,676 --> 00:18:04,536 All right. 448 00:18:04,536 --> 00:18:06,726 So next, I think we saw this last time. 449 00:18:06,726 --> 00:18:07,616 View Did Load. 450 00:18:07,916 --> 00:18:10,086 We saw this in our no Nib example, I believe. 451 00:18:10,546 --> 00:18:12,706 View Did Load, if we read the documentation, 452 00:18:12,706 --> 00:18:13,916 is just a method that's called 453 00:18:13,916 --> 00:18:16,466 when the View Did Load, so aptly named. 454 00:18:16,676 --> 00:18:18,736 And what does this guy seem to be doing? 455 00:18:19,626 --> 00:18:22,856 It's wrapping a bit, but it's about four lines of code total. 456 00:18:22,856 --> 00:18:27,256 >> It's adding the edit button. 457 00:18:27,426 --> 00:18:28,996 >> Yeah, it seems to be adding the edit button. 458 00:18:28,996 --> 00:18:32,286 So first we called the parents a met version of the method, 459 00:18:32,286 --> 00:18:33,726 and if we read the documentation, 460 00:18:33,726 --> 00:18:35,236 we will be reminded typically, 461 00:18:35,356 --> 00:18:37,636 be sure to call the parent before you do your own thing. 462 00:18:37,976 --> 00:18:41,716 Self.Navigation.Left Button Bar Item, I don't really know 463 00:18:41,716 --> 00:18:43,936 where this comes from, but I can probably guess 464 00:18:44,086 --> 00:18:46,466 that because we're implementing a subclass 465 00:18:46,466 --> 00:18:47,946 of the UITableViewController, 466 00:18:48,246 --> 00:18:53,516 presumably a UITableView has a property called navigation item. 467 00:18:53,776 --> 00:18:57,006 And that navigation item refers to the little blue or gray bar 468 00:18:57,006 --> 00:18:58,626 at the top of this kind of application, 469 00:18:58,886 --> 00:19:03,176 and .Left Button Item refers to -- .Left Bar Button Item, 470 00:19:03,176 --> 00:19:04,436 refers to the thing at top left, 471 00:19:04,836 --> 00:19:06,336 and we seem to be storing what there? 472 00:19:06,516 --> 00:19:10,316 Self.Edit Button Type Item, whatever that happens to be, 473 00:19:10,596 --> 00:19:13,666 and then UI Button Item, add button, so if we read this, 474 00:19:13,666 --> 00:19:16,736 we're apparently instantiating a UI Bar Button Item, 475 00:19:16,936 --> 00:19:20,236 allocating it, initializing it with this thing, 476 00:19:20,236 --> 00:19:22,176 UI Bar Button System Add. 477 00:19:22,436 --> 00:19:25,296 So there's a lot of code there that's not all that interesting 478 00:19:25,296 --> 00:19:28,046 to dwell on now, but if you think back to what's going on, 479 00:19:28,176 --> 00:19:32,046 this is really just the code version of going to something 480 00:19:32,046 --> 00:19:35,276 like my Nib, opening up the toolbar over here, 481 00:19:35,446 --> 00:19:39,366 scrolling down to the objects down here, and if we scroll, 482 00:19:39,366 --> 00:19:44,516 scroll, scroll, scroll, we'll eventually find Navigation Bar 483 00:19:44,686 --> 00:19:47,846 and Navigation Item, so what I'm doing, a code is the equivalent 484 00:19:47,846 --> 00:19:50,346 of dragging and dropping this into the user interface, 485 00:19:50,346 --> 00:19:52,126 much like we were doing last week. 486 00:19:52,506 --> 00:19:53,506 So that's -- that's all. 487 00:19:53,506 --> 00:19:55,386 The magic that we've been taking for granted of dragging 488 00:19:55,386 --> 00:19:58,516 and dropping is now being implemented more lower level 489 00:19:58,516 --> 00:19:59,476 in code. 490 00:20:00,046 --> 00:20:00,596 All right. 491 00:20:00,596 --> 00:20:02,856 So let's not worry too much about the user interface 492 00:20:02,856 --> 00:20:05,436 because that's not all that interesting 493 00:20:05,436 --> 00:20:06,516 at the end of the day. 494 00:20:06,856 --> 00:20:09,586 Let me just point out a few 495 00:20:09,586 --> 00:20:11,556 of the additional methods we've implemented. 496 00:20:11,786 --> 00:20:14,096 These are methods that we've implemented because we need 497 00:20:14,096 --> 00:20:16,726 to implement table related functionality. 498 00:20:16,986 --> 00:20:18,116 One of these is super simple. 499 00:20:18,436 --> 00:20:20,776 The method called Number Of Sections In TableView, 500 00:20:20,776 --> 00:20:22,826 if you read the documentation, its purpose in life is 501 00:20:22,826 --> 00:20:25,816 to return a number, namely how many rows should there be 502 00:20:25,816 --> 00:20:28,666 in the table, so that the operating system knows 503 00:20:28,666 --> 00:20:30,576 when to stop rendering rows. 504 00:20:30,886 --> 00:20:33,316 So in this case, we've just returned -- sorry. 505 00:20:33,966 --> 00:20:35,326 Not rows, sections. 506 00:20:35,726 --> 00:20:38,666 So sections are groupings of rows together, 507 00:20:38,666 --> 00:20:41,156 and if you have an iPhone and you go to your settings menu, 508 00:20:41,386 --> 00:20:44,166 you'll see that there are rows in your settings menu, 509 00:20:44,166 --> 00:20:46,676 but they're typically clustered with some kind of bold header. 510 00:20:46,846 --> 00:20:48,226 That's referring to a section. 511 00:20:48,226 --> 00:20:49,516 We had no such aesthetics here, 512 00:20:49,516 --> 00:20:52,166 so we just have one massive section, so I've hardcoded -- 513 00:20:52,166 --> 00:20:55,216 may have hardcoded the value of one in this template. 514 00:20:55,436 --> 00:20:58,816 So Next, TableView, Number Of Rows In Section. 515 00:20:59,336 --> 00:21:03,036 So this is the method that tells the program how many rows are -- 516 00:21:03,036 --> 00:21:04,376 should actually be in that table, 517 00:21:04,376 --> 00:21:06,216 how many dates have been added to the table. 518 00:21:06,216 --> 00:21:08,656 But what is Underscore Objects.Count? 519 00:21:08,836 --> 00:21:10,406 Where did that come from? 520 00:21:10,406 --> 00:21:14,456 >> It probably holds the information for the rows. 521 00:21:14,456 --> 00:21:17,006 >> Yeah, it probably holds the information for the rows 522 00:21:17,006 --> 00:21:20,156 because again, think about -- recall the difference between C 523 00:21:20,156 --> 00:21:21,736 and V, Controller and View. 524 00:21:22,046 --> 00:21:25,736 The View may very well render what looks like a table, 525 00:21:26,006 --> 00:21:28,336 but if there's any data that you're rendering, 526 00:21:28,336 --> 00:21:31,166 it's the Controller's job in life to actually keep track 527 00:21:31,166 --> 00:21:33,376 of that and just pass it to the View. 528 00:21:33,566 --> 00:21:36,686 So we shouldn't be storing those dates in the View per se. 529 00:21:36,686 --> 00:21:39,286 We should be storing all of those dates after every click 530 00:21:39,286 --> 00:21:42,076 of the plus button somewhere inside of my Controller, 531 00:21:42,236 --> 00:21:43,686 and then just handing it to the View. 532 00:21:43,896 --> 00:21:46,476 So Underscore Objects, if we glance back at the top 533 00:21:46,476 --> 00:21:50,126 of the file, was actually declared up here, 534 00:21:51,276 --> 00:21:54,066 and I've declared an NS mutable array. 535 00:21:54,126 --> 00:21:56,586 What's the difference between mutable array and NS array? 536 00:21:56,586 --> 00:21:57,536 >> You can modify it? 537 00:21:57,536 --> 00:21:58,186 >> You can modify it. 538 00:21:58,186 --> 00:21:59,876 So it's mutable in that you can change it. 539 00:21:59,876 --> 00:22:01,906 You can add, remove to and from it. 540 00:22:02,356 --> 00:22:05,836 So I've done At Interface Master ViewController open paren, 541 00:22:05,836 --> 00:22:08,656 closed paren, so again, we've already did that, I thought. 542 00:22:08,966 --> 00:22:10,496 In the .H file, we had 543 00:22:10,496 --> 00:22:12,916 At Interface MasterViewController open 544 00:22:12,916 --> 00:22:13,626 curly brace. 545 00:22:13,626 --> 00:22:16,376 Why have we repeated ourselves and added these parentheses? 546 00:22:16,376 --> 00:22:21,116 >> For it to be private? 547 00:22:21,116 --> 00:22:24,096 >> For it to be private or to the illusion of privacy. 548 00:22:24,096 --> 00:22:27,786 So we've used an unnamed category here, 549 00:22:27,786 --> 00:22:29,626 so recall that categories are just ways 550 00:22:29,626 --> 00:22:31,116 of grouping related functions. 551 00:22:31,116 --> 00:22:33,956 But the world, as a convention, has adopted it as a means 552 00:22:33,956 --> 00:22:36,436 of approximating the idea of private methods 553 00:22:36,436 --> 00:22:39,276 and private data members, private only in the sense 554 00:22:39,316 --> 00:22:42,836 that they are not being declared to the world in the .H file, 555 00:22:42,836 --> 00:22:45,136 because .H files can be imported by other people, 556 00:22:45,136 --> 00:22:48,086 which means other people would see our implementation details. 557 00:22:48,336 --> 00:22:49,706 But they're nonetheless adding it 558 00:22:49,706 --> 00:22:51,156 to the class Master ViewController, 559 00:22:51,156 --> 00:22:52,866 because it's inside of this declaration. 560 00:22:53,256 --> 00:22:55,956 So we apparently have an NS mutable array Underscore 561 00:22:55,956 --> 00:22:58,336 Objects, but where is that guy first used? 562 00:22:58,336 --> 00:23:02,536 Well, let me scroll down, and scroll down, and scroll down, 563 00:23:03,146 --> 00:23:08,096 and it looks like, let's see, where's our Underscore Objects? 564 00:23:08,096 --> 00:23:08,886 >> [Inaudible audience response]. 565 00:23:08,886 --> 00:23:13,196 >> Ah, there we go. 566 00:23:13,196 --> 00:23:15,506 Exactly. So here we have a method. 567 00:23:15,506 --> 00:23:18,236 Insert New Object colon. 568 00:23:18,666 --> 00:23:21,666 So what do you think is inducing this method to be called, 569 00:23:21,666 --> 00:23:22,856 based on what we've seen thus far? 570 00:23:23,416 --> 00:23:26,116 >> [Inaudible] the plus button? 571 00:23:26,116 --> 00:23:28,516 >> So pitting the plus button, and how was that done? 572 00:23:28,516 --> 00:23:30,476 Was it done in Interface Builder, or... 573 00:23:30,936 --> 00:23:34,396 So insert new object. 574 00:23:34,396 --> 00:23:37,596 So again, let's -- let's just do a little highlight and copy. 575 00:23:37,596 --> 00:23:38,906 Let's see where it -- oh, interesting. 576 00:23:39,186 --> 00:23:39,996 So View Did Load. 577 00:23:39,996 --> 00:23:41,296 We didn't finish that story. 578 00:23:41,556 --> 00:23:44,456 We didn't -- we -- Apple did not use Interface Builder teams 579 00:23:44,456 --> 00:23:45,516 to wire things up. 580 00:23:45,516 --> 00:23:47,506 They didn't -- done it all in low-level code, 581 00:23:47,796 --> 00:23:50,666 so in View Did Load, we started telling that story in terms 582 00:23:50,666 --> 00:23:51,736 of the Left Button Bar Item. 583 00:23:51,736 --> 00:23:54,256 If we go a little deeper, notice what's happening here. 584 00:23:54,556 --> 00:23:57,746 When we declared this UI Bar Button Item and allocate it 585 00:23:57,926 --> 00:24:01,446 and initialize it, we're choosing -- this is a constant, 586 00:24:01,446 --> 00:24:04,236 this very long word UI Bar Button System Item Add, 587 00:24:04,276 --> 00:24:07,176 is just the atrociously named constant for the plus icon. 588 00:24:07,266 --> 00:24:08,056 That's all that's doing. 589 00:24:08,056 --> 00:24:08,676 It's aesthetic. 590 00:24:08,676 --> 00:24:11,906 But we're saying Target colon Self Action 591 00:24:11,906 --> 00:24:13,846 at Selector Insert New Object. 592 00:24:14,176 --> 00:24:16,346 So first of all, what does Action colon 593 00:24:16,346 --> 00:24:19,306 at Selector Insert New Object doing functionally? 594 00:24:19,426 --> 00:24:26,406 >> It's just a message that should be sent 595 00:24:26,406 --> 00:24:27,606 when it's -- the action happens. 596 00:24:27,606 --> 00:24:28,016 >> Exactly. 597 00:24:28,016 --> 00:24:29,686 When some action happens, which in this case is going 598 00:24:29,686 --> 00:24:32,226 to be the touching of the button, 599 00:24:32,226 --> 00:24:34,166 that's the default behavior for one of these buttons 600 00:24:34,166 --> 00:24:35,656 when it's clicked by a user's finger, 601 00:24:35,896 --> 00:24:38,246 what message do you want to send to an object? 602 00:24:38,246 --> 00:24:40,566 You want to send this message: Insert New Object. 603 00:24:40,736 --> 00:24:43,116 Put another way, what method do you want to call. 604 00:24:43,676 --> 00:24:46,826 And to which object will that message be passed? 605 00:24:47,166 --> 00:24:49,166 On which object will that method be called? 606 00:24:49,676 --> 00:24:51,426 >> The target. 607 00:24:51,546 --> 00:24:52,176 >> The targets. 608 00:24:52,636 --> 00:24:56,636 So Target colon Self means this class, this object, 609 00:24:57,006 --> 00:25:00,126 and that is why slightly more lower 610 00:25:00,126 --> 00:25:01,946 in the screen we have an implementation 611 00:25:01,946 --> 00:25:03,886 of the method that we want to call. 612 00:25:04,186 --> 00:25:07,176 So as an aside, the reason that we have this funky syntax, 613 00:25:07,176 --> 00:25:09,446 at Selector open paren closed paren, 614 00:25:09,736 --> 00:25:13,026 is so that it's clear what the name of the message is 615 00:25:13,026 --> 00:25:14,776 that you want to send, because we've seen methods 616 00:25:14,776 --> 00:25:15,836 that have colons in them. 617 00:25:16,056 --> 00:25:18,276 And it would just get very complicated, 618 00:25:18,276 --> 00:25:20,906 if not impossible, to parse the string. 619 00:25:21,146 --> 00:25:24,396 If you had Action colon Insert New Object colon, where -- 620 00:25:24,396 --> 00:25:26,066 which colon belongs to what? 621 00:25:26,066 --> 00:25:27,466 So that's the idea of At Selector. 622 00:25:27,466 --> 00:25:28,686 It's just a syntactic thing. 623 00:25:29,046 --> 00:25:31,246 So that means when you click that plus button, 624 00:25:31,246 --> 00:25:34,266 this guy is actually called so, in answer to the question, 625 00:25:34,266 --> 00:25:37,206 where is the objects NS mutable array coming from? 626 00:25:37,366 --> 00:25:38,796 We instantiate it lazily. 627 00:25:38,876 --> 00:25:42,446 The first time we need it, we check does it exist? 628 00:25:42,696 --> 00:25:46,256 If it doesn't exist, that is if Underscore Objects equals nil, 629 00:25:46,546 --> 00:25:49,056 we're going to go ahead and instantiate an NS mutable array 630 00:25:49,056 --> 00:25:51,146 and then we're going to start populating it. 631 00:25:51,306 --> 00:25:53,346 And at this point, if you start to read through the code, 632 00:25:53,346 --> 00:25:54,636 you'll see a couple new features. 633 00:25:54,636 --> 00:25:56,636 There's this notion of the Index Path, 634 00:25:56,636 --> 00:25:58,686 which is something specific to these UI Table Views. 635 00:25:58,956 --> 00:26:02,816 A path is just a couple of numbers, two numbers together. 636 00:26:02,816 --> 00:26:04,756 A section and a row. 637 00:26:05,116 --> 00:26:06,936 So an index path is just an object 638 00:26:06,936 --> 00:26:09,746 that contains those two values, and if you keep reading further 639 00:26:09,746 --> 00:26:12,456 in the code, you'll see that this is the function 640 00:26:12,456 --> 00:26:14,826 that actually does the generation of an insertion 641 00:26:14,826 --> 00:26:17,596 of the date into that actual Table View. 642 00:26:18,316 --> 00:26:18,426 Yeah. 643 00:26:19,706 --> 00:26:22,536 >> First of all, say we have a property 644 00:26:22,606 --> 00:26:26,396 for the objects variable. 645 00:26:26,446 --> 00:26:32,186 What would be -- would be cost if you used the alternative? 646 00:26:32,186 --> 00:26:32,326 [Inaudible]? 647 00:26:32,326 --> 00:26:34,136 >> Good question. 648 00:26:34,136 --> 00:26:39,626 So suppose we had declared objects as a property. 649 00:26:40,326 --> 00:26:42,326 There would be a couple of implications. 650 00:26:42,326 --> 00:26:45,466 One, we could do Self.Objects and mutate it that way. 651 00:26:45,746 --> 00:26:48,076 On the other hand, so could anyone else who happens 652 00:26:48,076 --> 00:26:51,376 to be importing, for instance, my.H file, 653 00:26:51,376 --> 00:26:52,556 if we declared the property there, 654 00:26:52,556 --> 00:26:53,896 but we don't have to declare there. 655 00:26:54,636 --> 00:26:59,716 You would get some marginally additional functionality 656 00:26:59,716 --> 00:27:03,136 because by default, the setter and/or the getter will often 657 00:27:03,136 --> 00:27:04,256 have additional code in them. 658 00:27:04,256 --> 00:27:05,856 For instance, if you've declared it to be atomic, 659 00:27:05,856 --> 00:27:07,836 it will have some additional code with the setter. 660 00:27:07,836 --> 00:27:08,916 The setter will, by default, 661 00:27:08,916 --> 00:27:11,416 make sure that you never set an object equal to itself, 662 00:27:11,476 --> 00:27:13,366 which can do some bad things circularly. 663 00:27:13,616 --> 00:27:14,966 So you would get some protections, 664 00:27:14,966 --> 00:27:15,626 but you pay a price. 665 00:27:15,626 --> 00:27:17,636 What's the downside? 666 00:27:17,636 --> 00:27:20,976 Do you -- would you conjecture of using a property 667 00:27:21,166 --> 00:27:23,636 to implement this container as opposed 668 00:27:23,636 --> 00:27:26,076 to just declaring a raw pointer like this? 669 00:27:26,416 --> 00:27:27,756 >> It takes longer? 670 00:27:27,756 --> 00:27:28,576 >> It takes longer. 671 00:27:28,576 --> 00:27:31,286 And we're talking, you know, a negligible amount of time 672 00:27:31,286 --> 00:27:33,116 for something like this where clearly, I, 673 00:27:33,116 --> 00:27:35,146 the human in the bottleneck for any slowness 674 00:27:35,146 --> 00:27:37,746 in this application, how quickly I can press, but in theory, 675 00:27:37,746 --> 00:27:39,446 that's why they've done it in this way. 676 00:27:39,486 --> 00:27:41,346 Just to -- we're the only ones using the property. 677 00:27:41,346 --> 00:27:42,226 Not the rest of the world. 678 00:27:42,406 --> 00:27:45,276 I know how to use it, I just don't need the marginal overhead 679 00:27:45,276 --> 00:27:46,586 of a setter and a getter. 680 00:27:47,176 --> 00:27:47,906 But a good question. 681 00:27:48,876 --> 00:27:51,416 Okay. So let's not spend too much time on the particulars 682 00:27:51,416 --> 00:27:54,566 of this specific application, but let's just scroll 683 00:27:54,566 --> 00:27:56,866 through lastly the other methods that might be here. 684 00:27:56,866 --> 00:28:01,226 So there's this one, TableView, Self or Row at Index Path, 685 00:28:01,396 --> 00:28:05,006 because this one method actually reveals an interesting design 686 00:28:05,006 --> 00:28:06,316 pattern that's not uncommon, 687 00:28:06,316 --> 00:28:07,876 especially for performance reasons. 688 00:28:08,146 --> 00:28:11,366 So TableView, Self or Row At Index Path, 689 00:28:11,366 --> 00:28:12,686 and then it's given an index path. 690 00:28:12,686 --> 00:28:14,126 The purpose in life of this method, 691 00:28:14,176 --> 00:28:17,146 if we read the documentation for the UITableView Parent Class, 692 00:28:17,816 --> 00:28:24,266 is that it is supposed to return a cell, a UITableView cell, 693 00:28:24,266 --> 00:28:26,206 so an object that represents a cell 694 00:28:26,206 --> 00:28:28,706 in a table configured exactly as we want it. 695 00:28:28,706 --> 00:28:31,396 And by configured, I mean what text do you want for the cell? 696 00:28:31,556 --> 00:28:33,326 What buttons do you want on the cell? 697 00:28:33,326 --> 00:28:35,006 What behavior do you want for that cell? 698 00:28:35,006 --> 00:28:37,896 So in short, this method is called when rendering this row, 699 00:28:37,896 --> 00:28:40,036 then this row, then this row, then this row, then this row, 700 00:28:40,316 --> 00:28:43,666 it is my job to tell iOS how I want each row 701 00:28:43,666 --> 00:28:44,986 to look and behave. 702 00:28:45,346 --> 00:28:46,666 So what's interesting, though, 703 00:28:46,666 --> 00:28:48,256 about this implementation is the following. 704 00:28:48,256 --> 00:28:52,726 One, we have this static pointer declared here, so identifier 705 00:28:52,726 --> 00:28:56,036 that points to a string that's statically declared as "cell." 706 00:28:56,036 --> 00:28:57,366 This is completely arbitrary. 707 00:28:57,366 --> 00:29:00,466 It could be "fu" or "bar" any word there, but it's going 708 00:29:00,466 --> 00:29:01,976 to be used in the following way. 709 00:29:02,316 --> 00:29:07,836 Down here, I declare UITableView Cell, TableView DQ Reusable Cell 710 00:29:07,836 --> 00:29:12,386 With Identifier "cell," "fu," whatever word you've chosen. 711 00:29:13,166 --> 00:29:14,326 So what is that doing? 712 00:29:14,326 --> 00:29:16,926 Well, I'm checking if cell equals Equals Nil, 713 00:29:17,136 --> 00:29:21,166 that means that there apparently was no reusable cell 714 00:29:21,166 --> 00:29:23,926 in my queue, so nothing came back. 715 00:29:24,556 --> 00:29:25,996 And so what do I proceed to do? 716 00:29:25,996 --> 00:29:27,986 Well, it looks like a common paradigm here. 717 00:29:28,016 --> 00:29:31,416 UITableView Cell, allocate it, then initialize it 718 00:29:31,416 --> 00:29:33,506 with some long crazy named constant, 719 00:29:33,706 --> 00:29:38,606 and also give it a re-use identifier of "cell," or "fu," 720 00:29:38,606 --> 00:29:39,776 whatever word you chosen. 721 00:29:40,056 --> 00:29:42,096 Then lastly, change the accessory type 722 00:29:42,426 --> 00:29:46,336 to be UITableView Cell Accessory Disclosure Indicator. 723 00:29:46,396 --> 00:29:46,856 What is that? 724 00:29:46,856 --> 00:29:49,746 It's like the little eye icon or similar on the screen. 725 00:29:50,346 --> 00:29:50,876 All right? 726 00:29:51,376 --> 00:29:54,796 So -- or rather, the little arrow that points to the right 727 00:29:54,856 --> 00:29:56,646 that we saw on the TableView when we were in the app. 728 00:29:56,986 --> 00:29:58,216 Then we proceed to do what? 729 00:29:58,466 --> 00:30:00,976 We grab the object at that particular row. 730 00:30:01,456 --> 00:30:04,496 We then update the text label on that cell 731 00:30:04,496 --> 00:30:07,216 to be whatever the description is of that object, so in short, 732 00:30:07,436 --> 00:30:08,616 the object that we put in that -- 733 00:30:08,616 --> 00:30:11,906 the object we put in objects was essentially a date, 734 00:30:12,736 --> 00:30:13,856 and then we're just adding 735 00:30:13,856 --> 00:30:16,786 that to the descriptive text on the cell itself. 736 00:30:17,356 --> 00:30:18,846 And then we return the cell. 737 00:30:19,146 --> 00:30:21,406 So most of that was just configuration details. 738 00:30:21,406 --> 00:30:23,336 Maybe new in terms of the code we're seeing, 739 00:30:23,496 --> 00:30:25,236 but not all that interesting except 740 00:30:25,236 --> 00:30:27,186 for this If condition here. 741 00:30:28,136 --> 00:30:31,596 What do you think the purpose is of the relative complexity 742 00:30:31,596 --> 00:30:32,766 of these several lines? 743 00:30:32,766 --> 00:30:33,716 Why this queue? 744 00:30:33,716 --> 00:30:35,116 Why this reusable thing? 745 00:30:35,686 --> 00:30:36,506 What's going on? 746 00:30:36,966 --> 00:30:38,886 >> Make sure you don't overwrite the cell, 747 00:30:38,886 --> 00:30:40,366 then just make sure it's unique. 748 00:30:40,366 --> 00:30:42,076 >> Okay, so make sure you don't overwrite a cell. 749 00:30:42,076 --> 00:30:43,086 Make sure it's unique. 750 00:30:43,086 --> 00:30:46,486 True, but we could do that by just allocating a new cell 751 00:30:46,626 --> 00:30:49,216 for every one of the dates in this table, or every one 752 00:30:49,216 --> 00:30:51,416 of the words that I want to put in this table. 753 00:30:52,726 --> 00:30:56,346 Why else might I be introducing this complexity of some kind 754 00:30:56,346 --> 00:30:58,246 of queue of reusable cells? 755 00:30:58,836 --> 00:31:01,696 >> Want to change the value inside? 756 00:31:02,036 --> 00:31:04,316 >> Want to change the value inside, so that's true, 757 00:31:05,126 --> 00:31:07,136 but why -- what's the motivation? 758 00:31:07,626 --> 00:31:10,626 Let me press further. 759 00:31:10,626 --> 00:31:14,216 Suppose that you can view 10 cells on the screen at once, 760 00:31:14,216 --> 00:31:15,896 based on the height of your iPhone and the height 761 00:31:15,896 --> 00:31:20,566 of your font, and you have allocated, let me say, 762 00:31:20,646 --> 00:31:23,526 if you want -- if you only can display 10 rows at a time 763 00:31:23,776 --> 00:31:25,606 but you've got 100 date because you've hit 764 00:31:25,606 --> 00:31:29,856 that button 100 times, technically only 10 765 00:31:29,946 --> 00:31:33,736 of those cells need to be in RAM at any given time, 766 00:31:33,876 --> 00:31:35,556 because the other 90 are down here. 767 00:31:35,556 --> 00:31:37,046 The user is not going to be able to see them, 768 00:31:37,046 --> 00:31:38,786 so why bother keeping them in memory? 769 00:31:40,196 --> 00:31:42,726 So if I give you that insight, 770 00:31:43,536 --> 00:31:45,536 why are we apparently using this trick? 771 00:31:45,826 --> 00:31:46,726 What's the motivation? 772 00:31:47,226 --> 00:31:47,356 Yeah. 773 00:31:47,776 --> 00:31:49,546 >> To make it faster and [inaudible]. 774 00:31:49,546 --> 00:31:49,936 >> Exactly. 775 00:31:49,936 --> 00:31:52,216 It all boils down to memory usage and memory management, 776 00:31:52,216 --> 00:31:54,956 so to your comment earlier about really the spirit 777 00:31:54,956 --> 00:31:56,586 of keeping memory usage low, 778 00:31:56,766 --> 00:31:59,366 you could absolutely just allocate 100 cells 779 00:31:59,366 --> 00:32:01,836 for 100 items, and frankly the user is probably not going 780 00:32:01,836 --> 00:32:04,086 to notice any latency when a scrolling through them, 781 00:32:04,086 --> 00:32:05,236 because 100 is not that big. 782 00:32:05,496 --> 00:32:06,856 But suppose for Evil Hangman, 783 00:32:06,856 --> 00:32:08,116 you decided to make an application 784 00:32:08,116 --> 00:32:10,646 that displays all 100,000 plus words at once, 785 00:32:10,646 --> 00:32:11,666 and you scroll through that. 786 00:32:12,016 --> 00:32:14,186 Then you probably will, depending on the hardware, 787 00:32:14,186 --> 00:32:15,906 start to notice some latency because there's 788 00:32:15,906 --> 00:32:18,786 so much RAM being taken up by all of those rows, 789 00:32:18,786 --> 00:32:20,556 and it's completely unnecessary. 790 00:32:20,556 --> 00:32:22,706 Of the hundred thousand, you can only see maybe 10 of them 791 00:32:22,706 --> 00:32:25,696 at once, so you only need to have 10 actually resident 792 00:32:25,696 --> 00:32:27,896 in memory at a time, so this queue is meant 793 00:32:27,896 --> 00:32:29,446 to be a performance optimization. 794 00:32:29,446 --> 00:32:31,706 So if you've ever use an iOS application that starts 795 00:32:31,706 --> 00:32:34,226 to feel very laggy for some reason, it's probably 796 00:32:34,226 --> 00:32:37,106 because they were trying to do too much, and potentially some 797 00:32:37,106 --> 00:32:39,886 of that work was unnecessary, as might be the case here. 798 00:32:40,176 --> 00:32:42,386 So this is illustrative of that kind of design paradigm, 799 00:32:42,386 --> 00:32:46,446 especially as your data sets get larger and larger. 800 00:32:47,926 --> 00:32:50,886 Okay. Let's not dwell too much on the other methods, 801 00:32:50,886 --> 00:32:53,716 but happy to take questions if they arise 802 00:32:53,716 --> 00:32:55,496 or are on your minds now. 803 00:32:57,236 --> 00:32:57,876 All right. 804 00:32:57,876 --> 00:32:59,516 So that just leaves us with one last class, 805 00:32:59,516 --> 00:33:00,816 the Detail ViewController. 806 00:33:01,016 --> 00:33:02,826 So this guy, if I go to the .H file, 807 00:33:03,116 --> 00:33:04,996 looks pretty uninteresting, except for the fact 808 00:33:04,996 --> 00:33:08,096 that he's got a UILabel and he's got a Detail Item. 809 00:33:08,326 --> 00:33:10,086 I also see mention of IBOutlet. 810 00:33:10,086 --> 00:33:10,696 What is that again? 811 00:33:11,296 --> 00:33:14,746 What's an IBOutlet? 812 00:33:15,656 --> 00:33:18,146 >> Reference to a thing that's declared in the Nib? 813 00:33:18,286 --> 00:33:18,846 >> Okay, good. 814 00:33:18,846 --> 00:33:21,046 So it's a reference to something that's declared in the neb, 815 00:33:21,046 --> 00:33:23,196 so it's a means of my code talking 816 00:33:23,196 --> 00:33:25,046 to my drag and drop interface. 817 00:33:25,046 --> 00:33:27,746 And in this case, the thing in question is UILabel, 818 00:33:27,946 --> 00:33:31,236 so how can I pull up Interface Builder and see that interface? 819 00:33:31,236 --> 00:33:33,226 What file do I want to click next to follow this bread -- 820 00:33:33,226 --> 00:33:33,926 this trail of breadcrumbs? 821 00:33:33,926 --> 00:33:35,176 >> Detail ViewController.Nib. 822 00:33:35,716 --> 00:33:40,536 >> Yeah, so Detail ViewController.Nib, 823 00:33:40,536 --> 00:33:43,156 and if I look there, it looks like indeed, 824 00:33:43,156 --> 00:33:45,336 someone has just dragged and dropped a UILabel. 825 00:33:45,336 --> 00:33:49,166 I know that because I can see its description down over here. 826 00:33:49,336 --> 00:33:52,366 And when in doubt, too, if I go to the right-hand panel and open 827 00:33:52,366 --> 00:33:55,346 that up, and notice that I'm on the Identity Inspector, 828 00:33:55,596 --> 00:33:57,616 Xcode has a habit of dumbing things 829 00:33:57,616 --> 00:34:01,416 down by saying Label hyphen Detail ViewController dot dot 830 00:34:01,416 --> 00:34:02,916 dot, when really that's not all 831 00:34:02,916 --> 00:34:04,126 that interesting programmatically. 832 00:34:04,126 --> 00:34:06,346 You want to know what type of object is that really, 833 00:34:06,586 --> 00:34:09,386 so in the Identity Inspector, which you can see at top right, 834 00:34:09,716 --> 00:34:12,546 you can see that, oh, the thing I've just clicked is actually an 835 00:34:12,546 --> 00:34:13,976 instance of UILabel. 836 00:34:13,976 --> 00:34:15,846 That is what I have dragged and dropped, and again, 837 00:34:15,846 --> 00:34:18,996 that's the connection between code, and the drag 838 00:34:18,996 --> 00:34:20,346 and drop interface here. 839 00:34:20,766 --> 00:34:23,386 So let's enter just one last question before we put this 840 00:34:23,716 --> 00:34:24,896 template aside. 841 00:34:25,236 --> 00:34:27,246 How do we somehow pass control off 842 00:34:27,246 --> 00:34:30,516 from the Master ViewController to the Detail ViewController? 843 00:34:30,516 --> 00:34:31,836 How do we make that transition? 844 00:34:32,736 --> 00:34:34,406 We haven't looked at the code yet per se, 845 00:34:34,406 --> 00:34:37,106 but where would you look if you wanted to answer that question? 846 00:34:37,336 --> 00:34:40,786 How does clicking on a cell lead to a state transition? 847 00:34:41,246 --> 00:34:45,346 What file should we look at? 848 00:34:45,606 --> 00:34:47,646 >> Do you look at the method that's called 849 00:34:47,646 --> 00:34:49,006 when it's actually clicked? 850 00:34:49,006 --> 00:35:02,226 >> Okay, so we want to look at the method that's called 851 00:35:02,976 --> 00:35:05,226 when it's actually clicked. 852 00:35:05,626 --> 00:35:10,396 And how can I chase down that answer? 853 00:35:10,396 --> 00:35:19,436 >> Ask in a selector into the constructor of one of the codes? 854 00:35:19,436 --> 00:35:19,936 >> Okay. 855 00:35:23,676 --> 00:35:25,116 >> [Inaudible] the Master ViewController.M. 856 00:35:25,116 --> 00:35:25,606 >> Okay. 857 00:35:25,606 --> 00:35:27,786 >> Hitting control X, control X is a selector. 858 00:35:27,786 --> 00:35:28,946 >> Selector, okay. 859 00:35:29,206 --> 00:35:33,336 So there's a selector for insert new object. 860 00:35:33,336 --> 00:35:34,766 We saw that before. 861 00:35:34,876 --> 00:35:36,916 Only one match. 862 00:35:37,646 --> 00:35:40,986 >> There should probably be a protocol somewhere 863 00:35:40,986 --> 00:35:43,056 that defines an interface between Master... 864 00:35:43,056 --> 00:35:44,406 >> Okay. So let's see. 865 00:35:44,406 --> 00:35:50,126 If I scroll down here, self a row, can edit row at index path, 866 00:35:50,126 --> 00:35:51,436 TableView Commit Editing Style. 867 00:35:51,436 --> 00:35:53,026 That doesn't sound right. 868 00:35:53,026 --> 00:35:54,676 Oh this one, interesting. 869 00:35:54,676 --> 00:35:56,186 And that's exactly right. 870 00:35:56,186 --> 00:35:57,166 What Peter proposed is 871 00:35:57,166 --> 00:36:00,466 that presumably there's some method that's defined, 872 00:36:00,496 --> 00:36:04,376 maybe in that protocol we saw at the very beginning of the story, 873 00:36:04,376 --> 00:36:09,476 that is what's called when a user clicks on the row. 874 00:36:09,476 --> 00:36:11,386 And indeed that's the case. 875 00:36:11,386 --> 00:36:13,436 It's -- this is a common paradigm, clicking on the row 876 00:36:13,436 --> 00:36:15,876 in a table, so Apple went ahead and implemented 877 00:36:16,646 --> 00:36:23,576 that base functionality for us, so if we want to listen 878 00:36:23,576 --> 00:36:26,386 for that key press on one of those rows, 879 00:36:26,386 --> 00:36:28,426 we apparently just have 880 00:36:28,426 --> 00:36:32,616 to implement a method called TableView Did Select Row 881 00:36:32,616 --> 00:36:33,036 at Index Path. 882 00:36:33,036 --> 00:36:35,276 So what's going on in there? 883 00:36:35,276 --> 00:36:37,866 Well, notice first, it takes two arguments. 884 00:36:37,866 --> 00:36:39,176 The first is a TableView, 885 00:36:39,176 --> 00:36:43,846 so that's what TableView did the user click on. 886 00:36:43,876 --> 00:36:47,266 Maybe there's multiple ones on this screen. 887 00:36:47,576 --> 00:36:50,416 And what, again to be clear, is an Index Path? 888 00:36:50,416 --> 00:36:51,346 >> Section and... 889 00:36:51,346 --> 00:36:52,896 >> Section and a row number. 890 00:36:52,896 --> 00:36:56,106 So it's going to be like zero comma something 891 00:36:56,166 --> 00:36:58,106 for the zero section, zero index, 892 00:36:58,106 --> 00:36:59,706 and the actual row number. 893 00:36:59,706 --> 00:37:00,076 All right. 894 00:37:00,076 --> 00:37:01,216 So what are we doing here? 895 00:37:01,586 --> 00:37:07,206 We again seem to be doing what's generally called lazy loading. 896 00:37:07,496 --> 00:37:10,346 If the Detail ViewController does not yet exist, if it's nil, 897 00:37:10,346 --> 00:37:11,876 what do we actually do? 898 00:37:12,156 --> 00:37:17,436 We allocate it by calling Detail ViewController Alloc, 899 00:37:17,436 --> 00:37:24,406 we initialize it with Nib name, Detail ViewController. 900 00:37:24,406 --> 00:37:29,186 Notice when you call this method, you don't say .XIB. 901 00:37:29,336 --> 00:37:35,266 Bundle is just referring to what folder is it in. 902 00:37:35,266 --> 00:37:39,186 We just say nil because it's in the default. 903 00:37:39,186 --> 00:37:43,596 Everything is organized at this top level. 904 00:37:43,636 --> 00:37:48,086 And so once these lines of code have executed, 905 00:37:48,386 --> 00:37:51,166 we now have a pointer to an object 906 00:37:51,166 --> 00:37:52,456 of type Detail ViewController. 907 00:37:52,456 --> 00:37:57,496 So we've got the thing in memory now, we just have to transition 908 00:37:57,496 --> 00:37:59,316 from the Master to the Detail. 909 00:37:59,316 --> 00:38:01,526 So what am I going to do next? 910 00:38:01,526 --> 00:38:02,646 NS Date Object object. 911 00:38:02,646 --> 00:38:07,106 So just to be clear, what is this next line of code doing? 912 00:38:07,106 --> 00:38:10,796 On the right-hand side, we have what type of object? 913 00:38:10,796 --> 00:38:12,566 What is Underscore Objects? 914 00:38:12,656 --> 00:38:13,236 >> A mutable array? 915 00:38:13,236 --> 00:38:14,276 >> An NS mutable array. 916 00:38:14,276 --> 00:38:19,946 So if we index into it at a current row, that's going 917 00:38:20,046 --> 00:38:22,966 to return an object of what type apparently? 918 00:38:22,966 --> 00:38:25,536 An NS date, and on the left-hand side, we're allocating what? 919 00:38:25,536 --> 00:38:27,336 What's the pop quiz here? 920 00:38:27,336 --> 00:38:27,936 >> A pointer. 921 00:38:28,226 --> 00:38:31,256 >> A pointer, good, to an object of type NS date. 922 00:38:31,736 --> 00:38:35,876 So we're not allocating an NS date, we're allocating a pointer 923 00:38:36,196 --> 00:38:39,776 to an NS date, so it's just 64 bits most likely, 924 00:38:39,776 --> 00:38:40,856 not the full-fledged object. 925 00:38:40,856 --> 00:38:44,466 Next we do Self.Detail ViewController. 926 00:38:44,466 --> 00:38:46,526 Detail ViewController. 927 00:38:47,046 --> 00:38:49,166 What is Self.Detail ViewController? 928 00:38:49,166 --> 00:38:50,236 Where did we see that before? 929 00:38:50,696 --> 00:38:51,996 >> Property? 930 00:38:51,996 --> 00:38:57,086 >> So it's a property that we declared earlier, 931 00:38:57,086 --> 00:38:58,146 and .Detail Item? 932 00:38:58,696 --> 00:39:00,146 Well, what's Detail Item? 933 00:39:00,146 --> 00:39:02,936 It's going to be set to the object. 934 00:39:03,216 --> 00:39:08,206 Where did I see Detail Item? 935 00:39:08,916 --> 00:39:12,506 If I go to Detail ViewController.H, 936 00:39:12,506 --> 00:39:16,196 Detail Item was apparently a property that I stored here. 937 00:39:16,196 --> 00:39:16,626 It's a type ID. 938 00:39:16,626 --> 00:39:17,226 What does ID mean? 939 00:39:17,226 --> 00:39:17,816 >> Any object. 940 00:39:17,816 --> 00:39:18,526 >> Any object. 941 00:39:18,586 --> 00:39:20,616 It's a pointer that could be nil, 942 00:39:20,616 --> 00:39:22,086 but it's a pointer to any object. 943 00:39:22,086 --> 00:39:24,126 So this is just a generic way. 944 00:39:24,126 --> 00:39:25,766 We could have been more explicit and stored NS dates. 945 00:39:25,766 --> 00:39:27,126 Whoever with this template decided 946 00:39:27,126 --> 00:39:28,096 to just genericize it a bit, 947 00:39:28,096 --> 00:39:29,156 so we're storing something of type ID there. 948 00:39:29,186 --> 00:39:30,476 So lastly in this line, we call Push ViewController 949 00:39:30,506 --> 00:39:30,866 Animated Yes. 950 00:39:30,896 --> 00:39:32,486 So the fact that it slides from left to right, as we can see, 951 00:39:32,516 --> 00:39:33,656 is the following -- is the result of the following. 952 00:39:33,686 --> 00:39:34,856 Notice the sexy left right behavior like that, 953 00:39:34,886 --> 00:39:36,296 but if I instead change the bullion yes to bullion no, 954 00:39:36,326 --> 00:39:37,436 stop the current running instance and rerun, 955 00:39:37,466 --> 00:39:38,456 and now go ahead and plus, plus, plus, 956 00:39:38,486 --> 00:39:39,206 click here, much less elegance. 957 00:39:39,236 --> 00:39:39,416 All right? 958 00:39:39,446 --> 00:39:40,376 That's what makes Apple devices Apple. 959 00:39:40,406 --> 00:39:41,396 The sexy little slides back and forth. 960 00:39:41,426 --> 00:39:41,606 All right. 961 00:39:41,636 --> 00:39:41,876 Questions? 962 00:39:41,906 --> 00:39:43,466 Okay. So you may never again use a Master Detail ViewController 963 00:39:43,496 --> 00:39:44,096 template, and that's fine. 964 00:39:44,126 --> 00:39:45,506 The goal of this was not to walk through just templates 965 00:39:45,536 --> 00:39:46,136 that Apple hands to us, 966 00:39:46,166 --> 00:39:46,946 but rather [inaudible] the design paradigms 967 00:39:46,976 --> 00:39:48,026 that they're leveraging as a result of this 968 00:39:48,056 --> 00:39:49,316 so that you can either start with something like this, 969 00:39:49,346 --> 00:39:50,906 or something simpler, like the simple Single View application, 970 00:39:50,936 --> 00:39:52,166 and begin to wire things together in the same way. 971 00:39:52,196 --> 00:39:53,336 And what this is particularly illustrative 972 00:39:53,366 --> 00:39:54,776 of is wiring stuff together, not using Interface Builder, 973 00:39:54,806 --> 00:39:55,706 and dragging and dropping blue lines, 974 00:39:55,736 --> 00:39:57,386 but writing much more code and doing it manually and precisely. 975 00:39:57,386 --> 00:39:57,453 >> [Inaudible audience question]. 976 00:39:57,453 --> 00:39:57,746 >> IB outlet in... 977 00:39:57,746 --> 00:39:57,813 >> [Inaudible audience response]. 978 00:39:57,813 --> 00:39:58,196 >> This guy over here? 979 00:39:58,226 --> 00:39:58,616 Ah, good question. 980 00:39:58,646 --> 00:39:59,366 So Detail Description Item. 981 00:39:59,396 --> 00:40:00,866 For some reason, the developer who wrote this template seems 982 00:40:00,896 --> 00:40:02,336 to have gotten bored with actually doing the wiring and -- 983 00:40:02,366 --> 00:40:03,896 rather the coding, and decided to wire it up so we can go 984 00:40:03,926 --> 00:40:04,976 to the Nib file for Detail ViewController. 985 00:40:05,106 --> 00:40:08,016 And if I control click on this thing, 986 00:40:08,016 --> 00:40:12,776 we will see that Detail Description Label is wired 987 00:40:12,776 --> 00:40:13,936 to file's owner. 988 00:40:14,016 --> 00:40:15,946 And who is the owner of this file apparently? 989 00:40:15,946 --> 00:40:21,046 >> Yourself, or the Controller. 990 00:40:21,126 --> 00:40:21,676 >> The Controller. 991 00:40:21,676 --> 00:40:25,316 The Detail ViewController, because recall, that's the guy 992 00:40:25,316 --> 00:40:30,046 that initialized the Nib in In It With Nib Names. 993 00:40:30,186 --> 00:40:32,316 So he is the file's owner, because he is the guy 994 00:40:32,316 --> 00:40:34,726 that called this Nib file to life. 995 00:40:35,896 --> 00:40:38,036 So that was the one instance of dragging and dropping. 996 00:40:38,036 --> 00:40:43,666 Everything else in the Master was done in code. 997 00:40:43,826 --> 00:40:45,646 >> Okay so that's why it's [inaudible]? 998 00:40:45,646 --> 00:40:46,356 >> Yes. Oh, I'm sorry. 999 00:40:46,356 --> 00:40:47,416 Missed that part of the question. 1000 00:40:47,416 --> 00:40:49,506 Yes, so if we go into Detail ViewController, 1001 00:40:49,506 --> 00:40:51,796 we have seen a slightly different feature here. 1002 00:40:51,796 --> 00:40:53,866 These attributes associated with properties, 1003 00:40:54,226 --> 00:40:59,926 the reason that this here is weak is that we do not want the, 1004 00:41:00,776 --> 00:41:02,786 what's the best way to say this. 1005 00:41:03,696 --> 00:41:06,816 This property in the Detail ViewController is not -- 1006 00:41:07,176 --> 00:41:10,376 is pointing to an object that doesn't need to be kept around, 1007 00:41:10,376 --> 00:41:13,506 particularly if the Detail ViewController, once it goes 1008 00:41:13,506 --> 00:41:15,486 out of scope, as by hitting the back button, 1009 00:41:15,686 --> 00:41:16,736 disappears from memory. 1010 00:41:16,986 --> 00:41:18,576 We don't want to have a strong reference 1011 00:41:18,576 --> 00:41:21,816 to the Detail Description Label lest 1012 00:41:22,036 --> 00:41:25,346 that blue line keep the Detail ViewController 1013 00:41:25,466 --> 00:41:27,536 in memory unnecessarily long. 1014 00:41:28,116 --> 00:41:29,926 So in this really -- boils down -- 1015 00:41:29,926 --> 00:41:31,396 the motivation for this is 1016 00:41:31,396 --> 00:41:33,306 because the Detail ViewController is coming 1017 00:41:33,306 --> 00:41:36,416 and going, we want iOS to be able to reclaim that memory, 1018 00:41:36,656 --> 00:41:39,776 and so we don't hang onto, in a strong way, these bluelines. 1019 00:41:41,206 --> 00:41:43,246 And that's the first instance I think we've actually seen 1020 00:41:43,246 --> 00:41:45,346 of that use of weak for that reason. 1021 00:41:45,696 --> 00:41:46,196 Good question. 1022 00:41:47,166 --> 00:41:47,796 All right, why don't we go ahead 1023 00:41:47,796 --> 00:41:48,956 and take our five-minute break here. 1024 00:41:48,956 --> 00:41:50,946 Will come back and start building something from scratch. 1025 00:41:51,326 --> 00:41:53,316 And we're back. 1026 00:41:53,916 --> 00:41:55,606 So recall that there's been a checkbox 1027 00:41:55,606 --> 00:41:56,736 that we haven't checked this far 1028 00:41:56,736 --> 00:41:58,596 because we've been using Nibs instead. 1029 00:41:58,596 --> 00:42:00,336 And Nibs are a deliberate design decision 1030 00:42:00,336 --> 00:42:02,736 because they've given us much more low level control 1031 00:42:02,966 --> 00:42:04,156 over our user interface, 1032 00:42:04,416 --> 00:42:07,136 but popular these days is another feature 1033 00:42:07,136 --> 00:42:09,506 that we keep unchecking, known as Storyboards. 1034 00:42:09,506 --> 00:42:11,946 Anyone familiar with these yet? 1035 00:42:12,896 --> 00:42:13,866 Used Storyboards? 1036 00:42:13,866 --> 00:42:15,836 If we check that, what we get out of the box? 1037 00:42:16,656 --> 00:42:18,766 So this is Apple's way of trying 1038 00:42:18,766 --> 00:42:20,706 to simplify the user interface process further, 1039 00:42:20,706 --> 00:42:24,226 at least for applications that follow some common iOS paradigms 1040 00:42:24,226 --> 00:42:26,646 like the TableView that we just saw, the Utility Application 1041 00:42:26,646 --> 00:42:31,656 that we just saw, and making it less necessary to write code 1042 00:42:31,806 --> 00:42:33,896 to somehow make ViewControllers interact. 1043 00:42:34,286 --> 00:42:37,586 So if we follow this next screen by clicking Next 1044 00:42:37,586 --> 00:42:40,296 with ViewStoryboards, what we'll get is an application 1045 00:42:40,296 --> 00:42:42,736 that looks a bit like this, and let me go ahead and open 1046 00:42:42,736 --> 00:42:47,826 up a different project called Storyboard from tonight's code, 1047 00:42:48,136 --> 00:42:54,216 and this will give us a view of exactly what's different. 1048 00:42:54,216 --> 00:42:57,576 In the Storyboard folder, the story begins as usual 1049 00:42:57,576 --> 00:43:01,146 with Main.M, and then up here we seem to have Main ViewController 1050 00:43:01,146 --> 00:43:03,596 and Flipside ViewController, so what I've done was start 1051 00:43:03,596 --> 00:43:06,066 with the -- which template as a starting point apparently? 1052 00:43:06,066 --> 00:43:06,306 >> Utility? 1053 00:43:06,726 --> 00:43:09,646 >> So the Utility Application. 1054 00:43:09,646 --> 00:43:12,836 And a couple of you did this I think accidentally maybe last 1055 00:43:12,986 --> 00:43:15,086 week when following along since it was pointed 1056 00:43:15,086 --> 00:43:18,216 out that your Nib file looked a little different, and it's -- 1057 00:43:18,216 --> 00:43:20,766 or your UI looked a little different. 1058 00:43:20,766 --> 00:43:24,956 And indeed, if we go to Main Storyboard.Storyboard, 1059 00:43:25,156 --> 00:43:27,156 we see a user interface that looks like this 1060 00:43:27,276 --> 00:43:29,976 for utility application, and it appears that we're seeing 1061 00:43:29,976 --> 00:43:32,876 like two Nibs simultaneously: the Main ViewController 1062 00:43:33,096 --> 00:43:34,876 and the Flipside ViewController's UI 1063 00:43:35,066 --> 00:43:35,896 in the same screen. 1064 00:43:35,896 --> 00:43:38,656 But they're somehow connected via this transition, 1065 00:43:38,926 --> 00:43:41,626 generally known as a segue, and indeed that's what it is, 1066 00:43:41,626 --> 00:43:43,156 because when you use a Storyboard, 1067 00:43:43,346 --> 00:43:46,556 you essentially get one master file for your user interface, 1068 00:43:46,766 --> 00:43:49,926 and you wire this up all within itself. 1069 00:43:50,006 --> 00:43:54,176 And you specify in code exactly what you want to happen 1070 00:43:54,176 --> 00:43:57,626 when A segues to B. So the one line of code we need 1071 00:43:57,626 --> 00:44:00,446 to draw attention to really is just this. 1072 00:44:00,446 --> 00:44:02,356 If I go into my Main ViewController, 1073 00:44:02,576 --> 00:44:04,836 notice that this is actually pretty straightforward. 1074 00:44:04,836 --> 00:44:07,206 I've simply implemented a separate method this time called 1075 00:44:07,206 --> 00:44:09,336 Prepare For Segue Sender, 1076 00:44:09,696 --> 00:44:11,436 and this is the method that's apparently going 1077 00:44:11,436 --> 00:44:15,146 to be called whenever the user induces a transition 1078 00:44:15,146 --> 00:44:17,716 from the first controller to the second controller, 1079 00:44:17,896 --> 00:44:19,156 and you can see what's doing -- 1080 00:44:19,156 --> 00:44:22,346 what it's doing here if segue identifier is equal 1081 00:44:22,346 --> 00:44:24,586 to the string "show alternate." 1082 00:44:24,976 --> 00:44:27,696 So this string, show alternate, is completely arbitrary. 1083 00:44:27,696 --> 00:44:29,486 Could have been fu, bar, baz, whatever. 1084 00:44:29,676 --> 00:44:31,526 But it's a string that we'll see elsewhere 1085 00:44:31,756 --> 00:44:34,416 and apparently what's happening, if that is the identifier 1086 00:44:34,416 --> 00:44:37,456 of the segue that the user wants to happen by having interacted 1087 00:44:37,456 --> 00:44:38,326 with the application, 1088 00:44:38,726 --> 00:44:42,096 we're going to call Destination ViewController 1089 00:44:42,096 --> 00:44:45,096 on the segue, set delegate to Self. 1090 00:44:45,516 --> 00:44:49,046 In other words, before the user transitions from this side 1091 00:44:49,656 --> 00:44:53,156 to this side, we apparently want to inform the segue 1092 00:44:53,156 --> 00:44:57,496 that the destination is going to be what ultimately? 1093 00:44:58,036 --> 00:45:01,186 Or rather, we want to inform the Destination ViewController 1094 00:45:01,546 --> 00:45:06,406 that its delegate is going to be Self, the main side. 1095 00:45:06,576 --> 00:45:07,996 So recall the same paradigm 1096 00:45:07,996 --> 00:45:09,836 in the Utility Application we played with in class 1097 00:45:10,016 --> 00:45:12,086 that you've probably begun with for Evil Hangman, 1098 00:45:12,086 --> 00:45:15,726 or are about to, whereby when you click that Done button, 1099 00:45:15,916 --> 00:45:18,306 you want the transition to go back and you need to know 1100 00:45:18,306 --> 00:45:20,006 to whom to return control, 1101 00:45:20,006 --> 00:45:21,626 in this case the Main ViewController. 1102 00:45:21,916 --> 00:45:23,036 So that begs the question, 1103 00:45:23,036 --> 00:45:24,856 where is this quoted string coming from? 1104 00:45:24,966 --> 00:45:26,596 Where is this identifier for the segue? 1105 00:45:26,596 --> 00:45:30,846 So if we go to the Storyboard, and I click on the segue itself, 1106 00:45:30,846 --> 00:45:34,046 not much happens over here, but notice that this is apparently 1107 00:45:34,046 --> 00:45:38,646 of type Modal Segue From Button, flip to Flipside ViewController. 1108 00:45:38,646 --> 00:45:39,866 That's the English friendly string. 1109 00:45:40,086 --> 00:45:42,936 I'm going to have to make my UI a bit of a mess and open up, 1110 00:45:43,606 --> 00:45:50,336 over here, the right hand panel, and with that segue selected, 1111 00:45:50,336 --> 00:45:54,356 if I go up here to the Attributes Inspector, 1112 00:45:54,536 --> 00:45:57,736 notice that the programmer who made this template, in this case 1113 00:45:57,736 --> 00:46:01,106 at Apple, to manually typed in an identifier of Show Alternate, 1114 00:46:01,296 --> 00:46:03,616 But again, that could have been fu, bar, any string there, 1115 00:46:03,616 --> 00:46:05,706 and that's to uniquely identify the transition. 1116 00:46:05,936 --> 00:46:07,516 So in short, if we want 1117 00:46:07,516 --> 00:46:09,796 to somehow wire together the user interface 1118 00:46:09,796 --> 00:46:11,986 in this different paradigm whereby both sides 1119 00:46:11,986 --> 00:46:14,476 of the application are in one file, we simply have 1120 00:46:14,476 --> 00:46:18,516 to define what happens when that transition occurs. 1121 00:46:18,516 --> 00:46:22,046 So I mention these now because if you want 1122 00:46:22,046 --> 00:46:24,216 to take things further, say for your own native application, 1123 00:46:24,216 --> 00:46:25,426 if you go that route for the third, 1124 00:46:25,746 --> 00:46:27,896 you'll find that this is a very common paradigm now 1125 00:46:27,896 --> 00:46:30,786 with iOS programming because it really eliminates a lot more 1126 00:46:30,786 --> 00:46:32,076 of the wiring that you need to do, 1127 00:46:32,076 --> 00:46:34,066 and it centralizes the UI in one place. 1128 00:46:34,266 --> 00:46:36,456 And as this picture kind of suggests, 1129 00:46:36,616 --> 00:46:39,366 if you have a particularly complex UI, like a menu, 1130 00:46:39,366 --> 00:46:42,406 and then a submenu, and other submenus and other submenus, 1131 00:46:42,656 --> 00:46:44,436 you can wire them all together 1132 00:46:44,466 --> 00:46:45,986 within the confines of the same tool. 1133 00:46:46,086 --> 00:46:47,306 And it's just a simplification. 1134 00:46:47,486 --> 00:46:47,596 Yeah. 1135 00:46:47,696 --> 00:46:56,026 >> Is there a disadvantage of wiring like the information 1136 00:46:56,026 --> 00:46:57,706 to the second page and then going back to the first page? 1137 00:46:57,706 --> 00:46:58,266 >> Good question. 1138 00:46:58,266 --> 00:46:59,156 Is there a disadvantage? 1139 00:46:59,156 --> 00:46:59,406 Not really. 1140 00:46:59,406 --> 00:47:01,656 The gripe people tend to have with Interface Builder 1141 00:47:01,656 --> 00:47:03,756 or using Nibs or Storyboards in this way is that you don't have 1142 00:47:03,756 --> 00:47:07,146 as much low-level control, and you can't necessarily -- 1143 00:47:07,446 --> 00:47:10,746 might take -- sometimes take more steps to implement 1144 00:47:10,896 --> 00:47:13,146 than you want, and once you start having to write code 1145 00:47:13,466 --> 00:47:15,966 to talk to your Nib files and whatnot, at that point a lot 1146 00:47:15,966 --> 00:47:18,006 of people feel, oh, I'll just do it all from scratch. 1147 00:47:18,326 --> 00:47:20,856 And so that's why we just saw in the Master View, 1148 00:47:20,856 --> 00:47:23,586 the Master Detail Application, the master was all code, 1149 00:47:23,756 --> 00:47:25,456 even though the detail used a bit of wiring, 1150 00:47:25,746 --> 00:47:28,126 and the no Nib example last week was just all code. 1151 00:47:28,376 --> 00:47:30,566 So it's just a trade-off, and a lot of people, 1152 00:47:30,626 --> 00:47:33,216 seasoned iOS developers tend to prefer just doing things 1153 00:47:33,216 --> 00:47:35,376 from scratch, and of course if you're bored 1154 00:47:35,596 --> 00:47:38,256 with IOS's built-in UI in aesthetics, you have to do it 1155 00:47:38,296 --> 00:47:40,136 from scratch if you want to layer things on top. 1156 00:47:40,786 --> 00:47:41,816 Good question. 1157 00:47:42,506 --> 00:47:43,156 All right. 1158 00:47:43,366 --> 00:47:46,286 So let's start something truly from scratch now, 1159 00:47:46,556 --> 00:47:49,776 and based on time, we can pull a pre-baked cake out of the oven, 1160 00:47:49,776 --> 00:47:52,286 namely implementing an automated teller machine. 1161 00:47:52,286 --> 00:47:55,366 So a cash machine, a bank machine, that simulates the idea 1162 00:47:55,366 --> 00:47:57,646 of depositing money into a bank account 1163 00:47:57,766 --> 00:47:59,316 and actually doing some math to keep track 1164 00:47:59,316 --> 00:48:00,596 of the total account balance. 1165 00:48:00,886 --> 00:48:03,426 So let me go ahead and create a new project. 1166 00:48:03,426 --> 00:48:05,676 We'll do this as a Single View application just 1167 00:48:05,676 --> 00:48:08,816 to keep the focus now on the logic and less on details 1168 00:48:08,916 --> 00:48:11,946 like the transitions between scenes, 1169 00:48:12,256 --> 00:48:13,506 and let's go ahead and start. 1170 00:48:13,646 --> 00:48:14,796 I'll call this ATM. 1171 00:48:14,796 --> 00:48:16,536 I'm not going to use Storyboards. 1172 00:48:16,536 --> 00:48:18,936 I'm going to use the lower-level Nib approach, 1173 00:48:18,936 --> 00:48:20,486 especially since we only need one anyway. 1174 00:48:20,486 --> 00:48:23,386 I'm going to go ahead and click next, save it on my desktop, 1175 00:48:23,956 --> 00:48:27,186 and now I get our standard files over here on the top left. 1176 00:48:27,186 --> 00:48:28,626 We could tell the story as before, 1177 00:48:28,626 --> 00:48:30,116 but it's probably getting a little bit redundant now. 1178 00:48:30,116 --> 00:48:32,786 Main.M somehow invokes the AppDelegate, 1179 00:48:32,786 --> 00:48:35,016 somehow invokes the ViewController and the UI 1180 00:48:35,016 --> 00:48:36,846 for the ViewController comes from the Nib. 1181 00:48:37,146 --> 00:48:38,966 So let's go ahead and create a little bit 1182 00:48:38,966 --> 00:48:42,106 of an interface here for my ATM. 1183 00:48:42,226 --> 00:48:44,686 So I'm going to go ahead and make my whole background white, 1184 00:48:44,686 --> 00:48:46,936 just because, and then, let's see. 1185 00:48:47,066 --> 00:48:50,426 I want my ATM to look more like maybe a calculator 1186 00:48:50,426 --> 00:48:52,856 with a total input field up here, 1187 00:48:53,016 --> 00:48:55,016 maybe a total account balance down here, 1188 00:48:55,016 --> 00:48:56,246 and then a whole bunch of numbers. 1189 00:48:56,616 --> 00:48:57,956 So let's start to wire this up. 1190 00:48:57,956 --> 00:49:01,956 I'm going to go ahead and have a UILabel up top here. 1191 00:49:01,956 --> 00:49:07,476 I'm going to drag it to be as wide as I -- as is recommended. 1192 00:49:07,476 --> 00:49:12,446 Let me go ahead and increase that font size to make it, 1193 00:49:12,576 --> 00:49:15,196 oh, let's say 36, okay. 1194 00:49:15,196 --> 00:49:16,836 Now we'll go ahead and make it a little bigger. 1195 00:49:18,046 --> 00:49:21,656 And now let me go ahead and do another label that's 1196 00:49:21,656 --> 00:49:23,086 down here toward the bottom. 1197 00:49:23,456 --> 00:49:25,286 This is going to be my -- actually, let's just copy 1198 00:49:25,286 --> 00:49:27,936 and paste this so we get the same font size more quickly. 1199 00:49:28,576 --> 00:49:29,866 I'm going to go down here. 1200 00:49:29,866 --> 00:49:32,136 This will be my balance. 1201 00:49:32,806 --> 00:49:33,336 All right. 1202 00:49:33,336 --> 00:49:36,006 So now I need a whole bunch of buttons to represent this thing. 1203 00:49:36,276 --> 00:49:38,426 So I'm going to go into my rounded rec'd [assumed spelling] 1204 00:49:38,426 --> 00:49:40,566 button here, and let's see. 1205 00:49:40,566 --> 00:49:44,616 This will be the number, let's see, let's go ahead 1206 00:49:44,616 --> 00:49:46,766 and match this lest we get it backwards. 1207 00:49:47,666 --> 00:49:51,886 Let's go in, to save time, to the ATM, Xcode Project, 1208 00:49:52,386 --> 00:49:54,986 and dot dot dot so that we don't spend all day dragging 1209 00:49:54,986 --> 00:49:55,726 and dropping. 1210 00:49:56,076 --> 00:49:58,416 Voila. Now I have this interface. 1211 00:49:58,516 --> 00:49:59,976 So what's now on this screen? 1212 00:50:00,066 --> 00:50:02,786 Well, I write a line of the text, so just by clicking 1213 00:50:02,786 --> 00:50:03,966 in the Attributes Inspector. 1214 00:50:04,236 --> 00:50:07,686 I centered this field here and I added another UILabel just 1215 00:50:07,686 --> 00:50:09,386 to stay balanced, just for user interface. 1216 00:50:09,386 --> 00:50:12,226 So there's one label, two labels, three labels. 1217 00:50:12,226 --> 00:50:14,286 So these aren't input text fields per se, 1218 00:50:14,286 --> 00:50:15,696 but they're sort of output displays. 1219 00:50:15,696 --> 00:50:18,706 So in my code, I can display what the user's typing here, 1220 00:50:18,926 --> 00:50:22,876 and I can display what the user has in their account down here. 1221 00:50:23,196 --> 00:50:25,386 All right, so what might I want to do next? 1222 00:50:25,386 --> 00:50:27,696 Well, the goal is I want the user to be able to type in, 1223 00:50:27,696 --> 00:50:31,936 like, five, zero, deposit, in order to deposit $50 in his 1224 00:50:31,936 --> 00:50:34,256 or her account, and then I want to see 50 down here. 1225 00:50:34,256 --> 00:50:37,346 And then if I then do 10, one, zero, deposit, 1226 00:50:37,346 --> 00:50:40,786 I want to see a total account balance of 60 down here. 1227 00:50:40,786 --> 00:50:43,736 So we need somehow -- we somehow need to represent a few things 1228 00:50:43,736 --> 00:50:44,536 that are going on here. 1229 00:50:44,536 --> 00:50:47,546 One, all of these buttons need to be somehow connected 1230 00:50:47,546 --> 00:50:50,206 to my code so that when I push the number five, 1231 00:50:50,496 --> 00:50:53,196 and then the number zero, a couple of things happen. 1232 00:50:53,196 --> 00:50:57,556 One, those numbers get saved in RAM somewhere; two, they display 1233 00:50:57,556 --> 00:51:00,286 like a calculator would, five, zero, up here, 1234 00:51:00,426 --> 00:51:03,096 so I somehow need my code to talk to my interface 1235 00:51:03,096 --> 00:51:04,556 which is going to require a IB... 1236 00:51:04,556 --> 00:51:04,706 >> Action? 1237 00:51:05,096 --> 00:51:12,826 >> In this case, if I want my code to talk to the UI 1238 00:51:12,826 --> 00:51:16,476 and IBOutlet, in that direction, by contrast, 1239 00:51:16,476 --> 00:51:20,696 when I push a button, I want to trigger an IBAction to my code. 1240 00:51:20,696 --> 00:51:22,856 So I have some blue lines going in both directions, 1241 00:51:22,856 --> 00:51:25,076 or we can do it purely in code, as we've seen, 1242 00:51:25,076 --> 00:51:27,576 and then I have two special buttons: deposit, of course, 1243 00:51:27,866 --> 00:51:29,526 and then the clear button. 1244 00:51:29,846 --> 00:51:33,426 So before we get there, I'm going to go ahead and propose, 1245 00:51:33,426 --> 00:51:34,626 let me roll back in time, 1246 00:51:34,626 --> 00:51:36,256 so here's where we were a moment ago. 1247 00:51:36,256 --> 00:51:39,436 And let's assume that we're seeing now the cake being made 1248 00:51:39,436 --> 00:51:41,566 and then finally we'll skip to the ending here. 1249 00:51:41,866 --> 00:51:44,426 So as we're making this thing, I've realized in the top left 1250 00:51:44,796 --> 00:51:48,366 that this is an opportunity to have a model, the M in MVC, 1251 00:51:48,626 --> 00:51:50,706 because this is like a mechanical machine, 1252 00:51:50,706 --> 00:51:52,426 or a digital machine, that somehow has 1253 00:51:52,426 --> 00:51:53,896 to store account balances. 1254 00:51:54,166 --> 00:51:56,686 So what might I want to model in this program? 1255 00:51:56,956 --> 00:51:58,206 Well, maybe the notion of an account. 1256 00:51:58,646 --> 00:52:00,376 In fact, an account, like a bank account, 1257 00:52:00,376 --> 00:52:04,646 could be modeled pretty well as an object or an instantiation 1258 00:52:04,646 --> 00:52:07,716 of some class, and inside of an account is going to be one 1259 00:52:07,716 --> 00:52:08,656 or more pieces of data. 1260 00:52:08,656 --> 00:52:09,786 And the only one I'm going to care 1261 00:52:09,786 --> 00:52:12,266 about for now is the account balance. 1262 00:52:12,726 --> 00:52:15,676 So in order to do this, I'm going to go up to an option 1263 00:52:15,676 --> 00:52:17,686 that we probably haven't used but it's pretty straightforward. 1264 00:52:17,686 --> 00:52:21,956 File New file, so not a new project, just create a new file. 1265 00:52:22,176 --> 00:52:24,366 And you'll see an interface that looks a little overwhelming 1266 00:52:24,366 --> 00:52:26,566 at first because there's a lot of options, 1267 00:52:26,806 --> 00:52:28,406 but really they're just different templates 1268 00:52:28,406 --> 00:52:29,906 by which to start a new file. 1269 00:52:30,046 --> 00:52:32,146 And all I'm going to want is an Objective-C Class. 1270 00:52:32,146 --> 00:52:34,936 So I'm going to go ahead and click next, and I'm going 1271 00:52:34,936 --> 00:52:36,396 to call this thing account. 1272 00:52:36,716 --> 00:52:39,506 It's asking me what does -- what should it be a subclass of. 1273 00:52:39,506 --> 00:52:40,256 NS Object is fine. 1274 00:52:40,256 --> 00:52:41,116 Every other thing -- 1275 00:52:41,116 --> 00:52:42,896 most everything descends from NS Object, 1276 00:52:43,166 --> 00:52:44,666 so that's fine for my purposes. 1277 00:52:44,666 --> 00:52:47,436 I'm going to go ahead and click next, going to go ahead 1278 00:52:47,436 --> 00:52:51,756 and click create, and voila, at the top left of my file, 1279 00:52:51,986 --> 00:52:55,736 I now have the ability to represent an account object. 1280 00:52:55,736 --> 00:52:57,156 So let's see what I've gotten for free. 1281 00:52:57,436 --> 00:53:01,696 In Account.H, I have interface, account descends from NS Object, 1282 00:53:02,256 --> 00:53:05,766 and in Account.M, I just have a blank implementation. 1283 00:53:06,056 --> 00:53:08,286 So now I have an opportunity, again for the first time, 1284 00:53:08,286 --> 00:53:10,916 to implement some notion of an account balance. 1285 00:53:10,916 --> 00:53:12,266 And I'm going to propose the following. 1286 00:53:12,516 --> 00:53:16,646 In my.H file, I'm going to propose a property that's going 1287 00:53:16,646 --> 00:53:19,866 to have, let's say, a sign, we'll come back to that 1288 00:53:19,866 --> 00:53:22,896 in a moment, non-atomic attributes. 1289 00:53:22,896 --> 00:53:25,546 I'm going to propose that this be an unsigned, 1290 00:53:25,726 --> 00:53:27,846 long, long balance. 1291 00:53:28,406 --> 00:53:30,186 So a couple details pop out here. 1292 00:53:30,186 --> 00:53:33,616 So one unsigned, just to be clear, 1293 00:53:33,616 --> 00:53:38,406 means that the value can only be... 1294 00:53:38,406 --> 00:53:38,546 >> [Inaudible audience response]. 1295 00:53:38,546 --> 00:53:40,966 >> Nonnegative, so it can include zeros, 1296 00:53:40,966 --> 00:53:42,256 so that's what unsigned would mean. 1297 00:53:42,496 --> 00:53:43,806 So long, long? 1298 00:53:44,036 --> 00:53:44,446 What's that? 1299 00:53:44,446 --> 00:53:45,406 What's the role there? 1300 00:53:45,406 --> 00:53:45,473 >> [Inaudible audience response]. 1301 00:53:45,473 --> 00:53:52,156 >> We want it to be 64-bit, so in this platform doing a long, 1302 00:53:52,156 --> 00:53:54,486 long gets me a 64-bit number, 1303 00:53:54,486 --> 00:53:56,066 and that just means it's pretty darn big. 1304 00:53:56,066 --> 00:53:58,656 I want to avoid what's generally called Integer Overflow, 1305 00:53:58,876 --> 00:54:01,916 whereby if we type in too big of a number, I don't want it 1306 00:54:01,916 --> 00:54:04,466 to roll over with this high probability just some 1307 00:54:04,466 --> 00:54:05,156 random number. 1308 00:54:05,156 --> 00:54:06,866 It turns out this is not an adequate defense. 1309 00:54:06,866 --> 00:54:09,386 We can still break this ATM and deposit an arbitrary amount 1310 00:54:09,386 --> 00:54:12,156 of money in our account pretty easily, but we'll see how to -- 1311 00:54:12,276 --> 00:54:14,266 we'll simulate that in a bit. 1312 00:54:14,506 --> 00:54:16,796 Non-atomic, this just has to do with multi-threading. 1313 00:54:16,796 --> 00:54:18,086 I'm writing very simple code here. 1314 00:54:18,086 --> 00:54:19,286 There's not going to be two threads trying 1315 00:54:19,286 --> 00:54:21,666 to touch the account at once, though there could be certainly 1316 00:54:21,666 --> 00:54:23,626 in a world with multiple ATM's on a network. 1317 00:54:23,766 --> 00:54:24,826 But we'll keep it simpler. 1318 00:54:25,056 --> 00:54:27,206 And a sign now is different. 1319 00:54:27,206 --> 00:54:29,726 Typically we've seen what attribute in lines like this? 1320 00:54:30,746 --> 00:54:30,836 Yeah. 1321 00:54:31,326 --> 00:54:31,566 >> Copy. 1322 00:54:32,136 --> 00:54:35,646 >> So, okay, we've seen copy, but more commonly thus far 1323 00:54:35,646 --> 00:54:39,476 in our examples, we've seen strong, or weak, in this case. 1324 00:54:39,476 --> 00:54:43,166 So a sign literally does just that. 1325 00:54:43,166 --> 00:54:45,966 It gives me a setter that literally moves a value 1326 00:54:45,966 --> 00:54:47,756 from the right-hand side of an expression 1327 00:54:47,756 --> 00:54:49,256 to the left-hand side. 1328 00:54:49,256 --> 00:54:51,416 There's no checking for duplicate values; 1329 00:54:51,696 --> 00:54:54,006 there's no deep copying of objects. 1330 00:54:54,006 --> 00:54:55,186 And this is perfectly fine 1331 00:54:55,186 --> 00:54:57,606 for what's generally called the Primitive, like a long, long. 1332 00:54:57,606 --> 00:54:59,486 A long, long is just 64 bits. 1333 00:54:59,566 --> 00:55:02,346 To copy 64 bits, you just assign it from the right to the left 1334 00:55:02,346 --> 00:55:04,096 with an equals sign in between. 1335 00:55:04,436 --> 00:55:07,066 So there's no need for strong or weak, which have to do 1336 00:55:07,066 --> 00:55:08,566 with objects and pointers. 1337 00:55:08,856 --> 00:55:11,306 A copy also has to do with objects and pointers. 1338 00:55:11,306 --> 00:55:14,216 Assign is just for Primitive, so that's all I've specified here. 1339 00:55:14,806 --> 00:55:17,486 Okay? And by default, is this read write, or read only? 1340 00:55:18,046 --> 00:55:20,386 >> Read write. 1341 00:55:20,456 --> 00:55:22,466 >> It's read write, which means I get a setter 1342 00:55:22,466 --> 00:55:24,136 and a getter automatically 1343 00:55:24,206 --> 00:55:25,756 by having declared this property here. 1344 00:55:26,016 --> 00:55:27,686 Okay, so we're going to keep the account simple. 1345 00:55:27,686 --> 00:55:29,096 We're not going to bother with account numbers 1346 00:55:29,096 --> 00:55:30,546 or names or any of that. 1347 00:55:30,656 --> 00:55:31,866 We're just going to keep it simple 1348 00:55:31,866 --> 00:55:35,806 with our placeholder there, and now in my implementation 1349 00:55:35,806 --> 00:55:39,196 of this object, I might want to do one thing. 1350 00:55:39,196 --> 00:55:41,596 So it turns out an NS Object, recall, 1351 00:55:41,906 --> 00:55:44,556 comes with some default functionality in the form of an 1352 00:55:44,556 --> 00:55:47,176 In It Method, and that In It Method is defined 1353 00:55:47,176 --> 00:55:49,996 in the NS Object class. 1354 00:55:49,996 --> 00:55:52,666 And typically that method does nothing by default, 1355 00:55:52,666 --> 00:55:54,426 but it's an opportunity for us to do something. 1356 00:55:54,746 --> 00:55:57,856 What might you want to do in the way of initialization 1357 00:55:57,856 --> 00:56:00,226 when you instantiate an account object for the first time? 1358 00:56:00,226 --> 00:56:02,836 >> Set an initial balance? 1359 00:56:02,956 --> 00:56:04,776 >> Yeah, so why don't we set an initial balance. 1360 00:56:05,006 --> 00:56:07,246 So the signature for an In It Method, 1361 00:56:07,246 --> 00:56:09,756 if you look at the documentations for NS Object, 1362 00:56:09,756 --> 00:56:12,876 or just in general, the convention in iOS is -- 1363 00:56:12,876 --> 00:56:16,346 or an object of C, is to have an instance method, 1364 00:56:16,446 --> 00:56:19,996 hence the hyphen, returns an ID, which is a pointer or nil, 1365 00:56:19,996 --> 00:56:22,076 and it's called In It, by convention. 1366 00:56:22,076 --> 00:56:24,806 So it's kind of like -- it's the initialization half 1367 00:56:24,806 --> 00:56:25,626 of a constructor. 1368 00:56:25,926 --> 00:56:27,556 An Alloc would be the other half. 1369 00:56:27,556 --> 00:56:32,166 Again a common paradigm is to say Now This If Self Gets Super 1370 00:56:32,216 --> 00:56:35,766 In It, so this is just a common way of saying, one, 1371 00:56:36,086 --> 00:56:38,566 call the parent classes implementation of In It; 1372 00:56:38,756 --> 00:56:40,906 make sure that it doesn't return nil, 1373 00:56:40,906 --> 00:56:42,926 because if it does return nil, I don't want it 1374 00:56:42,926 --> 00:56:44,916 to start doing work unnecessarily lest I 1375 00:56:44,916 --> 00:56:45,796 create problems. 1376 00:56:46,046 --> 00:56:48,046 And now if all is well, 1377 00:56:48,046 --> 00:56:51,726 I'm going to do Self.Balance gets zero, 1378 00:56:52,206 --> 00:56:54,766 and then I need to return myself. 1379 00:56:56,006 --> 00:56:56,696 So that's it. 1380 00:56:56,796 --> 00:56:58,236 If I deleted all of this, 1381 00:56:58,406 --> 00:57:01,856 we wouldn't be initializing the Primitive to a known value, 1382 00:57:02,166 --> 00:57:04,236 so this way, we have a default value 1383 00:57:04,236 --> 00:57:05,246 or we could be nice, right? 1384 00:57:05,246 --> 00:57:06,016 If the first time you sign 1385 00:57:06,016 --> 00:57:07,556 up for a bank account you get some free gift, 1386 00:57:07,556 --> 00:57:09,496 maybe you get $00 in your account, 1387 00:57:09,496 --> 00:57:10,756 and we could do that right here. 1388 00:57:10,916 --> 00:57:11,186 Yes. 1389 00:57:11,406 --> 00:57:14,976 >> Why do you have to do super Alloc and In It? 1390 00:57:14,976 --> 00:57:19,656 >> Super Alloc and In -- because that would be bad, because when 1391 00:57:19,656 --> 00:57:22,456 In It is called, Alloc has already been called. 1392 00:57:22,976 --> 00:57:25,086 So the convention is call Alloc, then In It, 1393 00:57:25,206 --> 00:57:28,476 so if In It called Alloc, that would be trying 1394 00:57:28,476 --> 00:57:29,796 to instantiate the object twice. 1395 00:57:30,436 --> 00:57:33,586 Good question. 1396 00:57:34,226 --> 00:57:34,596 All right. 1397 00:57:34,826 --> 00:57:35,766 So that's it. 1398 00:57:35,766 --> 00:57:40,326 This is a super, super simple model, if you will, 1399 00:57:40,326 --> 00:57:41,756 but it's representative of how we could go 1400 00:57:41,756 --> 00:57:43,066 about encapsulating information. 1401 00:57:43,066 --> 00:57:45,476 It may be in a fancier world, this information would come 1402 00:57:45,476 --> 00:57:48,266 from a database, and if it did, it could go in this model code. 1403 00:57:48,266 --> 00:57:50,266 But we're going to just as an abstraction 1404 00:57:50,266 --> 00:57:52,676 for what an actual account balance is. 1405 00:57:53,016 --> 00:57:54,396 So now, what more do we have to do? 1406 00:57:54,396 --> 00:57:56,586 Well, let me jump back to the pre-baked version 1407 00:57:56,586 --> 00:57:57,656 that looks now like this. 1408 00:57:58,016 --> 00:58:00,586 Notice that at top left I have the exact same code 1409 00:58:00,586 --> 00:58:01,516 that I wrote in advance. 1410 00:58:01,516 --> 00:58:02,896 I have a property called balance, 1411 00:58:03,106 --> 00:58:04,546 and I have an implementation of In It. 1412 00:58:04,986 --> 00:58:07,346 So if we go back to the Nib, I also did a few things 1413 00:58:07,346 --> 00:58:10,086 in advance consistent with what we said was necessary. 1414 00:58:10,086 --> 00:58:16,176 One, I wired all of the buttons to my code u IBActions, 1415 00:58:16,696 --> 00:58:21,246 and I wired my code to two different UILabels via IB... 1416 00:58:21,746 --> 00:58:21,946 >> Outlets. 1417 00:58:22,506 --> 00:58:22,926 >> Outlets. 1418 00:58:22,926 --> 00:58:24,386 So two directions. 1419 00:58:24,386 --> 00:58:26,836 Now how can I check what directions they went in? 1420 00:58:26,836 --> 00:58:28,536 Well, let me go ahead and choose the number seven, 1421 00:58:28,816 --> 00:58:32,656 and notice that if I hold control and click on there, 1422 00:58:32,946 --> 00:58:35,016 there's a whole bunch in this drop-down, 1423 00:58:35,016 --> 00:58:37,276 but the interesting one, recall from last week, 1424 00:58:37,276 --> 00:58:40,396 is Touch-Up Inside, that's this act, and the result 1425 00:58:40,396 --> 00:58:41,826 of that is to do what? 1426 00:58:41,886 --> 00:58:42,976 Files Owner Digit? 1427 00:58:42,976 --> 00:58:45,446 What could that mean? 1428 00:58:45,446 --> 00:58:45,626 >> [Inaudible audience response]. 1429 00:58:45,626 --> 00:58:47,756 >> Call a method called Digit on what object? 1430 00:58:48,286 --> 00:58:48,916 >> File's owner. 1431 00:58:48,916 --> 00:58:51,086 >> On the file's owner, which in this case is going to be? 1432 00:58:51,086 --> 00:58:51,416 >> ViewController. 1433 00:58:52,446 --> 00:58:53,426 >> ViewController. 1434 00:58:53,426 --> 00:58:56,256 Exactly. So I'm in the ViewController, class is Nib, 1435 00:58:56,256 --> 00:58:58,906 and the file's owner is going to be the .M file, 1436 00:58:58,906 --> 00:59:02,616 so let's take a look at the .M file and indeed, there is, 1437 00:59:02,616 --> 00:59:06,306 nested among a few other methods, a method called Digit. 1438 00:59:06,616 --> 00:59:08,426 So I've declared this as an Instance Method. 1439 00:59:08,826 --> 00:59:11,486 It returns an IBAction by convention, 1440 00:59:11,486 --> 00:59:13,216 which is just synonymous with? 1441 00:59:14,446 --> 00:59:16,206 Remember your lower level C details? 1442 00:59:17,356 --> 00:59:17,956 Just void. 1443 00:59:18,186 --> 00:59:20,166 Just returns void, which means it returns nothing, 1444 00:59:20,406 --> 00:59:22,986 and it takes a pointer called sender, 1445 00:59:23,036 --> 00:59:24,736 and what is that going to be a pointer to? 1446 00:59:24,736 --> 00:59:26,396 >> The button that was pressed? 1447 00:59:26,556 --> 00:59:27,516 >> The button that was pressed. 1448 00:59:27,516 --> 00:59:28,246 So this is my way 1449 00:59:28,246 --> 00:59:31,116 of programmatically knowing what button was actually pressed. 1450 00:59:31,426 --> 00:59:34,306 So here's a -- a bit of a trick that we've leveraged 1451 00:59:34,306 --> 00:59:35,846 with the UIView class. 1452 00:59:36,086 --> 00:59:39,496 Notice in this first line of code, I'm doing the following. 1453 00:59:39,976 --> 00:59:43,346 On the left-hand side, I instantiate what? 1454 00:59:43,346 --> 00:59:46,186 >> Pointer to a UI Button? 1455 00:59:46,306 --> 00:59:48,806 >> Good. Pointer to a UI Button, and I keep asking this question 1456 00:59:48,806 --> 00:59:51,536 so that the answer is not allocate a UI Button, 1457 00:59:51,536 --> 00:59:52,206 which is not the case. 1458 00:59:52,206 --> 00:59:54,356 I've allocated a pointer to a UI Button. 1459 00:59:54,626 --> 00:59:56,286 On the right-hand side, what have I done? 1460 00:59:57,436 --> 00:59:59,956 >> Casting the center variable to a UI button... 1461 01:00:00,126 --> 01:00:00,716 >> Casting. 1462 01:00:00,716 --> 01:00:01,346 >> ...per style 1463 01:00:01,606 --> 01:00:02,236 >> Exactly. 1464 01:00:02,236 --> 01:00:05,736 So this is a C-Style cast whereby senders type? 1465 01:00:05,736 --> 01:00:08,896 I don't really know because I declared it as an argument 1466 01:00:09,006 --> 01:00:12,526 of a type ID, I don't actually really know what its type is, 1467 01:00:12,736 --> 01:00:16,136 so therefore I don't necessarily know what methods I can call 1468 01:00:16,136 --> 01:00:19,226 on it, and therefore Xcode doesn't know whether or not 1469 01:00:19,226 --> 01:00:22,226 to yell at me if I try calling a method maybe that doesn't exist. 1470 01:00:22,566 --> 01:00:25,186 It's okay to send messages to objects even 1471 01:00:25,186 --> 01:00:27,306 if they don't respond to them, but if I really want 1472 01:00:27,306 --> 01:00:31,476 to leverage my compiler in my ID here, it's nice if they can yell 1473 01:00:31,476 --> 01:00:34,296 at me when I'm do stupid things, so I can explicitly say 1474 01:00:34,296 --> 01:00:37,356 that sender is of type UI Button so that now, anything I do 1475 01:00:37,356 --> 01:00:40,646 with B will be known by Xcode as referring to a button. 1476 01:00:41,356 --> 01:00:41,456 Yeah. 1477 01:00:41,816 --> 01:00:43,006 >> Is there a difference doing in-line? 1478 01:00:43,006 --> 01:00:51,016 Like where you use [inaudible], cast B to the sender 1479 01:00:51,336 --> 01:00:51,726 to [inaudible] up there? 1480 01:00:51,896 --> 01:00:52,616 >> Good question. 1481 01:00:52,616 --> 01:00:54,006 That would be perfectly fine. 1482 01:00:54,006 --> 01:00:58,646 You could do this, let me scroll over, your code just starts 1483 01:00:58,646 --> 01:01:01,026 to look a little less readable, but that's perfectly fine, 1484 01:01:01,026 --> 01:01:02,426 and there's another way we could do this. 1485 01:01:02,616 --> 01:01:05,276 We don't strictly have to say ID up here. 1486 01:01:05,276 --> 01:01:08,176 We could do this and then eliminate this line altogether 1487 01:01:08,176 --> 01:01:09,316 and just refer to sender, 1488 01:01:09,496 --> 01:01:11,856 and the only reason I left it this way is really just 1489 01:01:11,906 --> 01:01:13,116 by convention. 1490 01:01:13,436 --> 01:01:18,266 Typically Apple always says ID as the type of the arguments, 1491 01:01:18,326 --> 01:01:21,366 and then casts it explicitly, but functionally it's the same. 1492 01:01:21,786 --> 01:01:22,866 The compiler won't yell at you. 1493 01:01:23,366 --> 01:01:28,446 Okay. So here now is a little grade school arithmetic that's 1494 01:01:28,446 --> 01:01:29,876 finally coming back to be useful. 1495 01:01:30,556 --> 01:01:32,666 Why does this line work? 1496 01:01:32,666 --> 01:01:35,276 Well, Self.Amount is referring to what? 1497 01:01:35,276 --> 01:01:37,326 I actually don't know what amount is. 1498 01:01:37,436 --> 01:01:39,066 So what is Self in this context? 1499 01:01:39,436 --> 01:01:40,596 What class are we inside of? 1500 01:01:42,046 --> 01:01:43,526 >> ViewController. 1501 01:01:43,596 --> 01:01:44,886 >> So this is the ViewController. 1502 01:01:44,886 --> 01:01:47,726 See I got out of sync here with my order of operations. 1503 01:01:47,726 --> 01:01:49,726 Let me go to the .H file and it looks 1504 01:01:49,726 --> 01:01:50,796 like there's a few things in here. 1505 01:01:50,796 --> 01:01:52,966 So let's actually pause for a moment and look at what's inside 1506 01:01:52,966 --> 01:01:54,476 of this particular ViewController. 1507 01:01:54,816 --> 01:01:57,966 So I have a property that's called account, 1508 01:01:58,386 --> 01:01:59,956 and it points to an account object. 1509 01:01:59,956 --> 01:02:01,236 Okay so there's my bank account. 1510 01:02:01,376 --> 01:02:05,706 There is my Controller linking to my M in MVC model. 1511 01:02:05,876 --> 01:02:08,416 So we saw that arrow promised in the picture earlier. 1512 01:02:08,776 --> 01:02:09,666 What's next? 1513 01:02:09,666 --> 01:02:10,626 A long, long amount. 1514 01:02:10,906 --> 01:02:13,166 I am not sure why there's an amount there, 1515 01:02:13,166 --> 01:02:14,086 so we'll come back to that. 1516 01:02:14,086 --> 01:02:15,616 There seems to be some duplication here 1517 01:02:15,616 --> 01:02:17,196 for some reason, but we'll come back to that. 1518 01:02:17,466 --> 01:02:19,876 And then here's the IBOutlet and the IBAction 1519 01:02:19,876 --> 01:02:20,836 that I mentioned earlier. 1520 01:02:20,836 --> 01:02:23,376 I apparently called it Balance Label, for the balance 1521 01:02:23,376 --> 01:02:25,266 at the bottom and Deposit Label 1522 01:02:25,356 --> 01:02:27,726 for the current number I'm typing in at the top, 1523 01:02:27,726 --> 01:02:28,696 just like a calculator. 1524 01:02:29,046 --> 01:02:31,626 And then I have some instance methods 1525 01:02:31,626 --> 01:02:32,916 that are declared down here. 1526 01:02:33,096 --> 01:02:34,666 As a spoiler, we're looking at Digit, 1527 01:02:34,666 --> 01:02:35,766 and this is the method that's going 1528 01:02:35,766 --> 01:02:37,836 to get invoked any time I touch a digit, a number. 1529 01:02:38,406 --> 01:02:40,456 Deposit is when I hit the green deposit button. 1530 01:02:40,686 --> 01:02:42,876 Clear is when I hit the red clear button. 1531 01:02:43,106 --> 01:02:45,456 And show is just a helper method I wrote 1532 01:02:45,456 --> 01:02:49,296 to keep my code organized and centralize all of the View code, 1533 01:02:49,296 --> 01:02:50,176 as we'll see in a moment. 1534 01:02:50,626 --> 01:02:53,256 So account, to be clear, is an account, 1535 01:02:53,406 --> 01:02:55,316 a pointer to an Account Object. 1536 01:02:55,316 --> 01:02:57,056 So now we go back to the .M file, 1537 01:02:57,246 --> 01:02:59,096 and now in Digit, what am I doing? 1538 01:02:59,546 --> 01:03:03,796 I'm storing Self.Amount, which was another unsigned long, long, 1539 01:03:04,606 --> 01:03:07,136 and I'm assigning it the return value 1540 01:03:07,136 --> 01:03:10,646 of Self.Amount times 10, plus B.Tag. 1541 01:03:10,646 --> 01:03:12,546 What do you think this is doing? 1542 01:03:12,946 --> 01:03:23,206 >> So amount just pulls what's the current -- 1543 01:03:23,206 --> 01:03:25,086 displayed right now. 1544 01:03:25,306 --> 01:03:25,536 >> Good. 1545 01:03:25,796 --> 01:03:31,386 >> So every time you click a button, you want to multiply it 1546 01:03:31,386 --> 01:03:34,846 by 10 because every time you click a button, 1547 01:03:34,886 --> 01:03:36,966 then you're shooting the digits over. 1548 01:03:36,966 --> 01:03:37,396 >> Exactly. 1549 01:03:37,396 --> 01:03:39,126 >> By one digit. 1550 01:03:39,126 --> 01:03:39,946 >> Exactly. 1551 01:03:39,946 --> 01:03:43,626 So when I referred to grade school earlier, I just meant 1552 01:03:43,626 --> 01:03:46,736 to the process of every time you multiply by ten, 1553 01:03:46,736 --> 01:03:48,286 it shifts the number over to the left 1554 01:03:48,286 --> 01:03:52,006 and that's effectively the behavior you want. 1555 01:03:52,006 --> 01:03:55,876 Every time you type in an additional number, 1556 01:03:56,826 --> 01:03:59,596 you want to shift the current numbers over 1557 01:03:59,596 --> 01:04:02,256 and put the new one there, and you can do that arithmetically 1558 01:04:02,366 --> 01:04:05,986 by just doing multiply by ten of the current value, 1559 01:04:05,986 --> 01:04:07,616 and then add in B.Tag. 1560 01:04:07,616 --> 01:04:08,146 So this is curious. 1561 01:04:08,146 --> 01:04:10,836 So B is a UI Button, a B UI Button is a descendant 1562 01:04:10,836 --> 01:04:15,326 from a class called a UIView, and it turns out, 1563 01:04:15,326 --> 01:04:17,196 if we read the documentation, 1564 01:04:17,196 --> 01:04:19,876 that a UIView has a property called, take a guess? 1565 01:04:19,876 --> 01:04:20,256 >> Tag. 1566 01:04:20,546 --> 01:04:23,076 >> Tag, which is just a number field. 1567 01:04:23,076 --> 01:04:26,256 It's an NS integer that you can use for whatever you want. 1568 01:04:26,256 --> 01:04:28,886 So for simplicity, what I decided to do here, 1569 01:04:28,886 --> 01:04:32,176 in my ViewController, is this. 1570 01:04:32,176 --> 01:04:36,976 Notice I've got the number seven here selected arbitrarily, 1571 01:04:37,066 --> 01:04:41,206 but we can see it on the other numbers as well. 1572 01:04:41,206 --> 01:04:45,936 If I go up to the Attributes Inspector, 1573 01:04:45,936 --> 01:04:50,236 notice that the contents of this button are the number seven, 1574 01:04:50,316 --> 01:04:52,576 but they could have been seven, 1575 01:04:52,666 --> 01:04:56,876 even though that would look a little strange, but this is only 1576 01:04:57,146 --> 01:04:59,316 to say that this is a string up here, 1577 01:04:59,316 --> 01:05:02,126 even though it looks like a number. 1578 01:05:02,126 --> 01:05:04,026 So that's the label of the button. 1579 01:05:04,026 --> 01:05:07,736 But if I scroll down, and scroll down, notice that under View, 1580 01:05:07,736 --> 01:05:10,816 which is just Apples way of categorizing attributes 1581 01:05:10,816 --> 01:05:13,226 that are specific to UIView Objects, 1582 01:05:13,226 --> 01:05:15,766 what field does a UIView apparently also have? 1583 01:05:15,766 --> 01:05:15,956 >> Tags. 1584 01:05:16,336 --> 01:05:16,836 >> It's a tag. 1585 01:05:16,836 --> 01:05:17,646 So tag, all lowercase. 1586 01:05:17,646 --> 01:05:20,586 This is just a property in the UIView class. 1587 01:05:20,826 --> 01:05:23,246 That's a number that you can use for whatever you want. 1588 01:05:23,246 --> 01:05:25,546 Typically, the cleanest way to use this is with constants 1589 01:05:25,546 --> 01:05:28,446 that are defined elsewhere, so that there's some kind 1590 01:05:28,446 --> 01:05:33,626 of programmatic mapping to the values, but for simplicity, 1591 01:05:33,626 --> 01:05:36,366 because this is a very simple application, 1592 01:05:36,366 --> 01:05:41,286 I decided to just go through each of my buttons and because 1593 01:05:41,286 --> 01:05:44,886 by wonderful convenience -- 1594 01:05:44,976 --> 01:05:47,686 coincidence, my buttons are meant to represent numbers, 1595 01:05:47,686 --> 01:05:51,316 I decided to assign each a tag that's identical to its label. 1596 01:05:51,316 --> 01:05:54,816 So I manually went in and made seven equal to seven, 1597 01:05:54,816 --> 01:05:57,646 eight is equal to eight, and notice that the number's going 1598 01:05:57,646 --> 01:06:00,466 to be changing there at top right. 1599 01:06:00,466 --> 01:06:03,856 If I click on two, it's two; zero, it's zero. 1600 01:06:03,856 --> 01:06:05,846 And then notice, deposit and clear are also zero, 1601 01:06:05,846 --> 01:06:11,336 but that's not a problem because I probably wired those guys 1602 01:06:11,336 --> 01:06:13,746 up to different methods so I don't have to worry 1603 01:06:14,446 --> 01:06:16,676 about confusing one zero for the other. 1604 01:06:16,726 --> 01:06:22,096 So if we go back to the button seven and control click on it, 1605 01:06:22,136 --> 01:06:23,836 notice that it will send the digit message 1606 01:06:23,836 --> 01:06:26,886 to file's owner whenever it's pressed up inside. 1607 01:06:26,886 --> 01:06:30,436 That means that digit gets called anytime I push a number, 1608 01:06:30,436 --> 01:06:38,996 and we saw on the .M file that that induces a little bit 1609 01:06:38,996 --> 01:06:42,676 of arithmetic where I multiply the current amount 1610 01:06:42,676 --> 01:06:44,556 in that top field by ten. 1611 01:06:44,556 --> 01:06:49,166 I then add B.tag to it, and then I call my Helper Method show. 1612 01:06:49,166 --> 01:06:52,676 And show, this is not something that comes up iOS. 1613 01:06:52,816 --> 01:06:54,706 I wrote it myself. 1614 01:06:54,706 --> 01:06:56,406 It was just my way 1615 01:06:56,406 --> 01:06:58,976 of centralizing all the code related to updating the UI, 1616 01:06:59,056 --> 01:07:00,446 and it looks like this. 1617 01:07:00,446 --> 01:07:01,756 I have two lines of code, even though they wrap, 1618 01:07:01,756 --> 01:07:05,076 and I'm setting my Self Balance Label Property, 1619 01:07:05,076 --> 01:07:06,996 the text thereof, to the result of calling NS strings, 1620 01:07:06,996 --> 01:07:09,446 String With Format Convenience Method, 1621 01:07:10,646 --> 01:07:13,306 passing in this very cryptic looking string, 1622 01:07:13,496 --> 01:07:23,746 Dollar Sign Percent L L U. What in the world does that mean? 1623 01:07:23,846 --> 01:07:26,226 What does the dollar sign mean? 1624 01:07:26,366 --> 01:07:27,726 >> Is it a dollar sign? 1625 01:07:27,846 --> 01:07:30,156 >> It's a dollar sign. 1626 01:07:30,156 --> 01:07:30,936 Money. Okay? 1627 01:07:31,146 --> 01:07:36,076 So percent L L U is a placeholder that represents? 1628 01:07:36,076 --> 01:07:37,526 >> Long, long unsigned value. 1629 01:07:37,526 --> 01:07:38,816 >> Exactly. 1630 01:07:38,816 --> 01:07:40,106 A long, long unsigned value. 1631 01:07:40,106 --> 01:07:41,766 So if you're familiar with C, 1632 01:07:41,766 --> 01:07:45,376 percent D is what you typically use for a decimal number, 1633 01:07:45,506 --> 01:07:49,626 but in this case, we want a long long and unsigned. 1634 01:07:49,626 --> 01:07:54,976 So cryptic, but it's perfect for what we want for our long, 1635 01:07:55,186 --> 01:07:57,936 long -- our unsigned long, long. 1636 01:07:57,936 --> 01:08:05,226 What do I want to paste into that value? 1637 01:08:05,226 --> 01:08:07,356 Comma Self.Account.Balance, 1638 01:08:07,356 --> 01:08:09,956 whose type is, again, long, long. 1639 01:08:09,956 --> 01:08:11,586 So I called this a Convenience Method. 1640 01:08:11,586 --> 01:08:15,516 In what sense is String With Format a Convenience Method? 1641 01:08:15,516 --> 01:08:16,916 What type of Method is String With Format, 1642 01:08:17,076 --> 01:08:18,776 apparently, based on the snippet? 1643 01:08:18,776 --> 01:08:19,156 >> A Class Method? 1644 01:08:19,196 --> 01:08:19,566 >> A class method. 1645 01:08:19,566 --> 01:08:22,646 Class method because we don't call Alloc. 1646 01:08:22,646 --> 01:08:27,766 You just call it directly so it's a Convenience Method, 1647 01:08:27,766 --> 01:08:32,476 excuse me, in the sense that you don't have to call Alloc, 1648 01:08:32,476 --> 01:08:36,216 you don't then have to call In It and jump through these hoops. 1649 01:08:36,216 --> 01:08:37,746 You just call this method. 1650 01:08:37,746 --> 01:08:41,106 And again, and I think we said this a couple weeks ago, 1651 01:08:41,106 --> 01:08:43,666 this is a very common paradigm in iOS. 1652 01:08:43,666 --> 01:08:46,916 If you have a class called NS String, or String, 1653 01:08:46,916 --> 01:08:48,926 having Convenience Methods that start 1654 01:08:48,926 --> 01:08:52,116 with roughly the class name and then With is a common way 1655 01:08:52,116 --> 01:08:55,646 of instantiating objects without calling Alloc, 1656 01:08:55,646 --> 01:08:58,126 so common paradigm is all. 1657 01:08:58,126 --> 01:09:00,526 Lastly, the thing done here is identical. 1658 01:09:00,526 --> 01:09:02,936 We're just doing the same thing with the current amount. 1659 01:09:02,936 --> 01:09:04,406 So notice the dichotomy. 1660 01:09:04,406 --> 01:09:06,256 I've got two variables called amount. 1661 01:09:06,256 --> 01:09:08,196 One is in my ViewController, and where's the other? 1662 01:09:08,196 --> 01:09:08,263 >> [Inaudible audience response]. 1663 01:09:08,263 --> 01:09:10,326 >> In the Account Object, and notice the distinction. 1664 01:09:10,326 --> 01:09:11,616 What's in my account is what I've already deposited, 1665 01:09:11,646 --> 01:09:12,786 but what's in the other variable called Amount, 1666 01:09:12,816 --> 01:09:14,286 which is in the ViewController, is just storing what value? 1667 01:09:14,316 --> 01:09:15,006 >> What the user has typed in. 1668 01:09:15,036 --> 01:09:15,966 >> With the user has typed in thus far. 1669 01:09:15,996 --> 01:09:16,686 So if we run this thing now, 1670 01:09:16,716 --> 01:09:17,946 even though we haven't seen quite all of the pieces, 1671 01:09:17,976 --> 01:09:19,086 and we pull up the actual user interface, 1672 01:09:19,116 --> 01:09:19,866 and I click the number seven, 1673 01:09:19,896 --> 01:09:20,736 that digit message has been sent. 1674 01:09:20,766 --> 01:09:22,056 We have done the math of multiplying zero by ten, 1675 01:09:22,086 --> 01:09:23,076 which is the default value, plus seven, 1676 01:09:23,106 --> 01:09:23,916 and then I've called the Show Method, 1677 01:09:23,946 --> 01:09:24,876 which updates the value to be seven. 1678 01:09:24,906 --> 01:09:26,286 But only once I click deposit here is the deposit 1679 01:09:26,316 --> 01:09:26,616 method called. 1680 01:09:26,646 --> 01:09:27,096 So let's check that. 1681 01:09:27,126 --> 01:09:28,716 If I go to the Nib, and I go to control click on deposit, 1682 01:09:28,746 --> 01:09:30,096 scroll down here, touch up inside is mapped to deposit, 1683 01:09:30,126 --> 01:09:31,326 so now, if I want to see what the positive does, 1684 01:09:31,356 --> 01:09:32,196 if I go into my.M and scroll 1685 01:09:32,226 --> 01:09:33,006 down to here, that is doing what? 1686 01:09:33,036 --> 01:09:34,236 Self.Account.Balance Plus Equals Self Amount, 1687 01:09:34,266 --> 01:09:35,016 so it's adding what's actually 1688 01:09:35,046 --> 01:09:36,366 in the Controllers variable to the ATMs variable. 1689 01:09:36,396 --> 01:09:37,596 What am I doing with Self.Amount Equals Zero? 1690 01:09:37,626 --> 01:09:38,616 Well, I'm just clearing my local value 1691 01:09:38,646 --> 01:09:39,906 and then I'm updating the UI by calling Show again. 1692 01:09:39,936 --> 01:09:41,316 So this is actually a really clean example of MVC 1693 01:09:41,346 --> 01:09:42,366 by keeping these barriers between everything. 1694 01:09:42,396 --> 01:09:43,356 The Controller's doing all of my logic 1695 01:09:43,386 --> 01:09:44,646 and my temporary arithmetic, but once I'm ready 1696 01:09:44,676 --> 01:09:45,816 to make the deposit do I talk to the model, 1697 01:09:45,846 --> 01:09:46,956 and only once I've done that do I show things 1698 01:09:46,986 --> 01:09:48,186 by having the Controller call on the View by way 1699 01:09:48,216 --> 01:09:48,876 of this method I called Show. 1700 01:09:48,906 --> 01:09:49,086 All right. 1701 01:09:49,116 --> 01:09:50,556 So which method is probably going to be pretty similar? 1702 01:09:50,586 --> 01:09:51,606 Clear? If we look at clear, super simple. 1703 01:09:51,636 --> 01:09:52,806 It's the result of having wired things together, 1704 01:09:52,836 --> 01:09:54,036 but suppose I've screwed up and I forgot to wire 1705 01:09:54,066 --> 01:09:55,116 up the Clear Method, which I can simulate 1706 01:09:55,146 --> 01:09:55,746 by clicking the X there. 1707 01:09:55,776 --> 01:09:56,856 And so now the clear button has no effect. 1708 01:09:56,886 --> 01:09:58,356 From what to what do I need to click and drag in order 1709 01:09:58,386 --> 01:09:59,526 to reconstruct that IBAction or IBOutlet? 1710 01:09:59,556 --> 01:09:59,976 First what is it? 1711 01:10:00,596 --> 01:10:00,916 >> IBAction? 1712 01:10:01,796 --> 01:10:02,766 >> IBAction? 1713 01:10:02,906 --> 01:10:06,476 What do I have to go -- do? 1714 01:10:06,476 --> 01:10:06,706 >> [Inaudible audience response]. 1715 01:10:06,706 --> 01:10:07,726 >> Click on the clear? 1716 01:10:07,726 --> 01:10:08,566 All right. 1717 01:10:08,566 --> 01:10:10,366 Holding control, go to where? 1718 01:10:10,606 --> 01:10:11,146 >> File's owner. 1719 01:10:11,396 --> 01:10:12,016 >> Files owner. 1720 01:10:12,016 --> 01:10:13,976 Let go. There I see a list of all 1721 01:10:13,976 --> 01:10:15,316 of the methods that I can call. 1722 01:10:15,316 --> 01:10:17,266 The one that doesn't have a hyphen means I just haven't 1723 01:10:17,266 --> 01:10:18,056 wired it up yet. 1724 01:10:18,166 --> 01:10:20,376 I'm going to go do that, and now we've fixed it. 1725 01:10:20,376 --> 01:10:23,766 Conversely, if I screwed up my label, which currently, 1726 01:10:23,996 --> 01:10:25,366 if I click on this with control, 1727 01:10:25,366 --> 01:10:28,286 is mapped to Deposit Label, how do I fix this? 1728 01:10:28,466 --> 01:10:30,286 Well, I can control click on my label, 1729 01:10:30,286 --> 01:10:32,596 go to files owner, and, hmm. 1730 01:10:34,936 --> 01:10:35,916 Just the other way. 1731 01:10:35,996 --> 01:10:38,496 So IBOutlets go from files owner to deposit. 1732 01:10:38,736 --> 01:10:40,986 There it is, Deposit Label, wire it up, 1733 01:10:40,986 --> 01:10:43,666 and now I've resurrected the actual interface. 1734 01:10:44,986 --> 01:10:45,946 Any questions? 1735 01:10:48,156 --> 01:10:48,996 All right. 1736 01:10:49,346 --> 01:10:51,256 So let me propose with this particular one, 1737 01:10:51,256 --> 01:10:53,376 especially when it comes time to your native applications, 1738 01:10:53,376 --> 01:10:55,446 if you want to start with something from scratch, 1739 01:10:55,836 --> 01:11:00,026 think about using that as the beginnings of an application 1740 01:11:00,026 --> 01:11:03,186 because it draws these fairly clear lines between MV and C, 1741 01:11:03,186 --> 01:11:06,306 which recall is just the picture that we looked at earlier, 1742 01:11:06,776 --> 01:11:08,986 and as well, last week. 1743 01:11:09,846 --> 01:11:10,176 All right. 1744 01:11:10,336 --> 01:11:11,656 So let's forge ahead to something's that going 1745 01:11:11,656 --> 01:11:13,216 to give us a new capability altogether. 1746 01:11:13,216 --> 01:11:15,916 Rather than focus on reinforcing some of the things we've done, 1747 01:11:16,206 --> 01:11:19,026 let's go ahead and consider this. 1748 01:11:19,026 --> 01:11:22,386 It turns out that there's a whole bunch of ways 1749 01:11:22,386 --> 01:11:24,886 that we can start storing information. 1750 01:11:24,886 --> 01:11:29,956 To date, we have not stored any information persistently 1751 01:11:30,166 --> 01:11:31,306 in a program that we've written. 1752 01:11:31,306 --> 01:11:32,666 Every time you quit the application, 1753 01:11:32,666 --> 01:11:34,616 any things that you've been storing in variables, 1754 01:11:34,616 --> 01:11:35,676 anything you've stored in properties, 1755 01:11:35,676 --> 01:11:36,796 just disappears altogether. 1756 01:11:36,796 --> 01:11:39,286 But it turns out, in iOS we can store things in a number 1757 01:11:39,286 --> 01:11:41,256 of formats, so we have things call Property Lists, 1758 01:11:41,256 --> 01:11:42,706 which we've actually encountered before. 1759 01:11:42,776 --> 01:11:45,866 Something called NS Defaults or settings, SQL Light, 1760 01:11:45,866 --> 01:11:48,526 XML or json, even something called Core Data, 1761 01:11:48,806 --> 01:11:49,706 so Property List. 1762 01:11:49,706 --> 01:11:50,766 We've seen those before. 1763 01:11:51,196 --> 01:11:53,246 What's a Property List, or P List, file? 1764 01:11:53,926 --> 01:11:55,746 .P List? Yeah. 1765 01:11:56,106 --> 01:11:58,116 >> It's a dictionary of strings. 1766 01:11:58,446 --> 01:11:58,796 >> Exactly. 1767 01:11:58,796 --> 01:11:59,846 Is the dictionary of strings. 1768 01:11:59,846 --> 01:12:02,396 It's a file containing key values pairs and we've seen this 1769 01:12:02,396 --> 01:12:05,876 in Xcode in the form of a nice little pretty table form 1770 01:12:05,876 --> 01:12:07,596 with keys on the left and values on the right, 1771 01:12:07,746 --> 01:12:09,006 but that's just the user-friendly way 1772 01:12:09,006 --> 01:12:11,386 of showing you what's really an XML file with data types 1773 01:12:11,416 --> 01:12:13,376 like strings and integers underneath the hood. 1774 01:12:13,696 --> 01:12:17,476 But it's useful, and if you've dived into Evil Hangman already, 1775 01:12:17,476 --> 01:12:20,306 you know that this is the format in which we've provided you 1776 01:12:20,306 --> 01:12:21,996 with a whole bunch of words. 1777 01:12:21,996 --> 01:12:24,086 It happens to be an XML file underneath the hood, 1778 01:12:24,296 --> 01:12:26,696 and you can see as much if you actually download that. 1779 01:12:26,696 --> 01:12:30,256 In fact, let's go over to the distribution code, 1780 01:12:30,256 --> 01:12:33,946 and if I go to CS76.net/projects, 1781 01:12:34,426 --> 01:12:38,096 and we have the Full Words dog P List file there. 1782 01:12:38,096 --> 01:12:43,796 If I try to open it in Xcode, it's going to open 1783 01:12:43,796 --> 01:12:46,746 in this big chart here, which is kind of misleading 1784 01:12:46,746 --> 01:12:50,466 because there aren't really keys called item zero item one. 1785 01:12:50,466 --> 01:12:52,826 This is just their way of representing an array 1786 01:12:53,136 --> 01:12:55,586 in this table format, but if I instead go 1787 01:12:55,586 --> 01:12:59,786 into my downloads folder here and I open up Words.P list with, 1788 01:12:59,786 --> 01:13:02,546 let's say, Text Wrangler, which is just a simple text editor, 1789 01:13:03,746 --> 01:13:06,956 we are going to see this, which is XML. 1790 01:13:06,956 --> 01:13:09,616 If unfamiliar, XML is like HTML but you get to make 1791 01:13:09,616 --> 01:13:10,726 up your own tag names, 1792 01:13:11,006 --> 01:13:13,736 and so here we have an element called Array, 1793 01:13:13,736 --> 01:13:15,386 and then a whole bunch of strings. 1794 01:13:15,386 --> 01:13:18,096 So that is what we have given you for this dictionary, 1795 01:13:18,096 --> 01:13:20,796 and there's thousands and thousands of lines here. 1796 01:13:21,006 --> 01:13:22,486 So this is actually a perfect candidate 1797 01:13:22,486 --> 01:13:24,476 if implementing a program that listed all these words, 1798 01:13:24,746 --> 01:13:27,666 not to keep all of them around in like UITable cells, 1799 01:13:27,666 --> 01:13:29,436 if you were using a TableViewController 1800 01:13:29,436 --> 01:13:30,406 like we did earlier. 1801 01:13:30,806 --> 01:13:34,546 So with regard to storage, Property Lists are nice 1802 01:13:34,546 --> 01:13:36,766 when at least you have static information that you want 1803 01:13:36,766 --> 01:13:38,336 to shift with your application. 1804 01:13:38,656 --> 01:13:41,796 But they can also be used effectively to store defaults. 1805 01:13:41,796 --> 01:13:45,186 You can store value pairs, even when an application quits, 1806 01:13:45,366 --> 01:13:49,656 and one of the things you'll get to use an Evil Hangman or dabble 1807 01:13:49,656 --> 01:13:52,656 with in lab is NS Defaults, which is an interface 1808 01:13:52,656 --> 01:13:55,826 for storing information persistently in applications 1809 01:13:55,826 --> 01:13:58,396 so that when it quits, you can actually reload those same 1810 01:13:58,396 --> 01:13:59,756 values after the fact. 1811 01:13:59,756 --> 01:14:02,216 So what kind of uses might persistent storage 1812 01:14:02,216 --> 01:14:03,566 like that have for an application? 1813 01:14:03,566 --> 01:14:06,486 Why is this useful? 1814 01:14:06,666 --> 01:14:10,026 >> If you got a call while playing your game, 1815 01:14:10,106 --> 01:14:13,176 then you could store data and when they hung 1816 01:14:13,176 --> 01:14:14,546 up the call, you could resume it. 1817 01:14:14,546 --> 01:14:15,026 >> Okay, good. 1818 01:14:15,026 --> 01:14:16,916 So if you got a phone call, it interrupted your game, 1819 01:14:16,916 --> 01:14:19,406 you could then reload the information that the game -- 1820 01:14:19,576 --> 01:14:20,786 the state that the game was in so 1821 01:14:20,786 --> 01:14:22,246 that you can continue playing it. 1822 01:14:22,586 --> 01:14:25,106 So to be honest, you probably don't need to use Property Lists 1823 01:14:25,106 --> 01:14:28,546 for that because so long as the application is backgrounded, 1824 01:14:28,546 --> 01:14:31,706 you can keep stuff in RAM still, unless the user quits, 1825 01:14:31,706 --> 01:14:32,656 in which case they're at a loss. 1826 01:14:32,656 --> 01:14:34,496 >> I was talking about NS Defaults. 1827 01:14:34,596 --> 01:14:35,166 >> Oh, I'm sorry. 1828 01:14:35,166 --> 01:14:37,336 So NS, okay so well, and even NS Defaults. 1829 01:14:37,336 --> 01:14:40,206 So NS Defaults are truly meant to be default values, 1830 01:14:40,836 --> 01:14:43,986 not state remembrance for the state of the game. 1831 01:14:44,246 --> 01:14:46,136 So defaults would be like do you want the sound 1832 01:14:46,136 --> 01:14:47,316 on or off by default? 1833 01:14:47,316 --> 01:14:49,846 Do you want -- what's your nickname by default? 1834 01:14:50,656 --> 01:14:52,646 So NS Defaults are good for things like that. 1835 01:14:52,646 --> 01:14:55,036 Configurable options that the user might change in the game. 1836 01:14:55,336 --> 01:14:56,726 Settings is just another UI. 1837 01:14:56,726 --> 01:14:59,416 A lot of applications, like in Evil Hangman, 1838 01:14:59,416 --> 01:15:01,676 will have settings built into the application, for instance 1839 01:15:01,676 --> 01:15:03,056 on the Flipside, and indeed that's 1840 01:15:03,056 --> 01:15:05,426 where you can store things like the preferred word length 1841 01:15:05,426 --> 01:15:09,866 and number of guesses, and in NS Defaults, if through that API, 1842 01:15:10,166 --> 01:15:12,996 which ends up writing a file into the iPhone or to the iPad 1843 01:15:13,106 --> 01:15:16,366 or the like, but you can also create write code, 1844 01:15:16,576 --> 01:15:19,526 that allows you to hook into the settings icon on the iPhone 1845 01:15:19,526 --> 01:15:21,846 or the iPad where you can move your settings there. 1846 01:15:22,106 --> 01:15:23,526 It's really just design decision. 1847 01:15:23,526 --> 01:15:25,316 What people tend to do for simple settings, 1848 01:15:25,316 --> 01:15:27,666 if you only have a few, they put them in the application itself. 1849 01:15:27,956 --> 01:15:29,476 If there's lots and lots of settings, 1850 01:15:29,476 --> 01:15:31,006 some people factor them out and put them 1851 01:15:31,006 --> 01:15:32,556 under the settings icon on the phone. 1852 01:15:32,556 --> 01:15:34,076 It's a little more annoying, though, because you have 1853 01:15:34,076 --> 01:15:36,976 to exit the application and go to it to actually get at them. 1854 01:15:36,976 --> 01:15:40,796 But you'll find that this is as easy as writing key value pairs 1855 01:15:40,796 --> 01:15:44,796 to an object, so more on that with Evil Hangman. 1856 01:15:45,016 --> 01:15:46,746 What's SQL Light, if familiar? 1857 01:15:47,286 --> 01:15:50,376 >> Like file SQL. 1858 01:15:52,416 --> 01:15:55,736 It stores a SQL accessible database in a [inaudible] file. 1859 01:15:55,846 --> 01:15:57,226 >> Exactly. 1860 01:15:57,226 --> 01:16:00,816 So SQL, a structured query language, is a database language 1861 01:16:00,816 --> 01:16:02,626 with which you can write information to a database 1862 01:16:02,626 --> 01:16:05,326 and read it, and use syntax that allows you 1863 01:16:05,326 --> 01:16:07,436 to search the database fairly easily. 1864 01:16:07,436 --> 01:16:10,036 You don't have to resort to linear search all of the time. 1865 01:16:10,396 --> 01:16:12,226 And it's nice because you don't need a server. 1866 01:16:12,226 --> 01:16:15,216 You don't need MySQL or Postgres or Oracle or anything like that. 1867 01:16:15,396 --> 01:16:17,336 You just store it in a binary file 1868 01:16:17,336 --> 01:16:19,486 in the same folder typically as your code, 1869 01:16:19,636 --> 01:16:23,656 and what SQL Light is, it's an API that lets you read and write 1870 01:16:23,736 --> 01:16:26,356 from that file using select and insert and delete 1871 01:16:26,356 --> 01:16:28,366 if you're familiar with that feature of SQL. 1872 01:16:28,676 --> 01:16:32,696 The catch is, in iOS, the SQL Light library is implemented not 1873 01:16:32,696 --> 01:16:36,416 in Objective-C but in C, which means the code looks horrific. 1874 01:16:36,416 --> 01:16:38,146 It's very useful, it's very powerful, 1875 01:16:38,146 --> 01:16:39,516 but it's also a bit arcane, 1876 01:16:39,696 --> 01:16:42,306 and so people typically use other constructs, 1877 01:16:42,306 --> 01:16:43,476 a couple of which we've discussed. 1878 01:16:43,866 --> 01:16:46,886 XML, meanwhile, or json, is typically used 1879 01:16:46,886 --> 01:16:50,236 when transporting information these days across the wire, 1880 01:16:50,236 --> 01:16:52,426 so Property List or XML, but if you were 1881 01:16:52,426 --> 01:16:54,426 to have your own arbitrary format, typically that's 1882 01:16:54,426 --> 01:16:56,976 for a game or a program that somehow grabs information 1883 01:16:56,976 --> 01:16:58,256 from a server on the Internet. 1884 01:16:58,506 --> 01:17:00,156 These are very useful data formats 1885 01:17:00,156 --> 01:17:01,436 for exchanging information. 1886 01:17:01,436 --> 01:17:04,176 And then finally there's Core Data, which is an iOS -- 1887 01:17:04,356 --> 01:17:06,346 which is an Apple SDK which allows you 1888 01:17:06,346 --> 01:17:08,936 to abstract the notion of a database altogether 1889 01:17:09,156 --> 01:17:12,486 and define your database schema, define the keys 1890 01:17:12,486 --> 01:17:13,936 and the values, the relations. 1891 01:17:13,936 --> 01:17:18,066 Among them, using a very graphical editor to wire things 1892 01:17:18,066 --> 01:17:19,356 up a little more high level. 1893 01:17:19,486 --> 01:17:20,656 And you had a question here. 1894 01:17:20,746 --> 01:17:25,276 >> Is it possible to query a regular expression in SQL light? 1895 01:17:25,276 --> 01:17:28,596 >> Is it possible to query a regular expression in SQL Light? 1896 01:17:28,976 --> 01:17:29,916 Simplified ones. 1897 01:17:29,946 --> 01:17:33,856 SQL supports like queries where you can use a subset 1898 01:17:33,856 --> 01:17:36,356 of Perl's regular expressions, or, which are common 1899 01:17:36,356 --> 01:17:37,386 in other languages as well. 1900 01:17:37,826 --> 01:17:38,496 So sort of. 1901 01:17:38,936 --> 01:17:40,876 Good question. 1902 01:17:41,256 --> 01:17:41,686 All right. 1903 01:17:41,686 --> 01:17:46,156 So let's actually -- let's go back over here and let's go 1904 01:17:46,156 --> 01:17:49,196 into tonight's sources, and let's go into P List. 1905 01:17:49,316 --> 01:17:54,156 So I, in advance, downloaded the P list file earlier 1906 01:17:54,436 --> 01:17:56,116 on my own computer over here. 1907 01:17:56,676 --> 01:17:57,266 Not that when. 1908 01:17:57,396 --> 01:17:59,356 So now if I go into P List, 1909 01:17:59,356 --> 01:18:02,676 and go into the distribution code here, we'll see some 1910 01:18:02,676 --> 01:18:04,026 of the usual friends, and let me go 1911 01:18:04,026 --> 01:18:06,716 into Main.M. Okay, no surprises there. 1912 01:18:06,976 --> 01:18:07,786 Let me next go 1913 01:18:07,786 --> 01:18:11,196 into AppDelegate.H. No surprises there. 1914 01:18:11,546 --> 01:18:14,746 AppDelegate.M. No surprises there. 1915 01:18:14,746 --> 01:18:16,016 It seems to be handing off control now 1916 01:18:16,016 --> 01:18:19,486 to ViewController.H. Really nothing going on there. 1917 01:18:19,896 --> 01:18:21,556 ViewController.M. Finally, 1918 01:18:21,776 --> 01:18:23,406 there's something going on in here. 1919 01:18:23,406 --> 01:18:23,996 But let's wait. 1920 01:18:23,996 --> 01:18:26,896 Let's go to the Nib file, and for some reason, 1921 01:18:26,896 --> 01:18:29,726 my example involves cities in California. 1922 01:18:30,026 --> 01:18:32,436 So this is always been a stupid feature of Interface Builder. 1923 01:18:32,436 --> 01:18:35,576 When you drag and drop a UITableViewController 1924 01:18:35,576 --> 01:18:38,416 into an application, rather than show you your data 1925 01:18:38,416 --> 01:18:41,396 or just blanks, they arbitrarily show you cities in California. 1926 01:18:41,396 --> 01:18:43,266 Those are not in the application itself. 1927 01:18:43,506 --> 01:18:44,326 It's like a screenshot 1928 01:18:44,326 --> 01:18:46,596 of someone else's application, but mildly confusing. 1929 01:18:46,976 --> 01:18:51,986 But if I now go back to my code, let's see what I'm doing. 1930 01:18:51,986 --> 01:18:53,116 So recall that we looked 1931 01:18:53,116 --> 01:18:55,866 at the master Detail Application earlier, 1932 01:18:55,866 --> 01:18:58,306 which was a little complex, and I've stolen some 1933 01:18:58,306 --> 01:18:59,926 of the simpler ideas from it, 1934 01:19:00,156 --> 01:19:03,226 just to implement the following application. 1935 01:19:03,226 --> 01:19:05,166 If I go ahead and click run up here, woops, 1936 01:19:05,746 --> 01:19:11,966 and let me quit the old simulator, and let me run this. 1937 01:19:12,166 --> 01:19:15,506 In the latest version of the simulator, 1938 01:19:15,506 --> 01:19:19,546 it's going to pop open, and you might see some familiar words. 1939 01:19:19,546 --> 01:19:22,716 So these are from our Property List called Small.P List, 1940 01:19:22,716 --> 01:19:24,586 which I downloaded from the courses website. 1941 01:19:24,796 --> 01:19:26,876 Recall that the product specification gives you a super 1942 01:19:26,876 --> 01:19:29,006 short list, just so you can tinker without worrying 1943 01:19:29,006 --> 01:19:30,326 about hundreds of thousands of words. 1944 01:19:30,606 --> 01:19:33,176 So that's just an XML file that I've literally dragged 1945 01:19:33,176 --> 01:19:34,676 and dropped into the project, 1946 01:19:34,806 --> 01:19:36,636 and somehow in code I'm opening this up. 1947 01:19:36,806 --> 01:19:36,986 Yes. 1948 01:19:37,486 --> 01:19:46,796 >> [Inaudible audience question]. 1949 01:19:47,296 --> 01:19:48,276 >> Yes, you should. 1950 01:19:48,276 --> 01:19:51,476 It's because I made these on another computer 1951 01:19:51,546 --> 01:19:55,686 and that one, there we go, yeah. 1952 01:19:55,786 --> 01:19:58,156 So with things like this, I'll go -- 1953 01:19:58,156 --> 01:19:59,166 I'll fix these and re-upload them 1954 01:19:59,166 --> 01:19:59,976 so you don't see these little warnings. 1955 01:20:00,046 --> 01:20:02,846 It's because the computer I was creating them 1956 01:20:02,846 --> 01:20:04,956 on was a slightly different version. 1957 01:20:05,106 --> 01:20:08,036 Short answer, your code should have no warnings, therefore do 1958 01:20:08,036 --> 01:20:08,836 as I say, not as I do. 1959 01:20:09,766 --> 01:20:11,046 But I will fix that. 1960 01:20:11,046 --> 01:20:13,856 Okay. So this P List file, I literally just dragged 1961 01:20:13,856 --> 01:20:16,476 and dropped into the supporting files folder, 1962 01:20:16,476 --> 01:20:17,476 but that's not really a folder. 1963 01:20:17,476 --> 01:20:19,416 I could have put it anywhere into the project, 1964 01:20:19,576 --> 01:20:22,796 and so that means all of the logic must be in this .M file. 1965 01:20:22,796 --> 01:20:23,876 So let's see what's going on. 1966 01:20:24,276 --> 01:20:25,856 This is my ViewController class. 1967 01:20:26,216 --> 01:20:28,606 I have chosen to implement this familiar method now, 1968 01:20:28,606 --> 01:20:31,396 In It With Nib Name Bundle, and what am I doing in there? 1969 01:20:31,396 --> 01:20:34,496 One, I'm calling the parent classes version of that method, 1970 01:20:34,726 --> 01:20:37,276 so that's familiar construct, checking it's return value 1971 01:20:37,276 --> 01:20:38,216 to make sure it's not nil, 1972 01:20:38,406 --> 01:20:39,996 and then I'm apparently loading words. 1973 01:20:40,176 --> 01:20:42,516 So how do you go about loading an XML file, 1974 01:20:42,516 --> 01:20:45,066 specifically a Property List, from your application 1975 01:20:45,066 --> 01:20:47,066 if you've dragged and dropped it in there or added it 1976 01:20:47,066 --> 01:20:48,836 by going to File Add File? 1977 01:20:49,196 --> 01:20:52,726 Well, I apparently call NS Bundle Main Bundle, so this -- 1978 01:20:52,886 --> 01:20:55,636 this is a way of saying to iOS, give me essentially the path 1979 01:20:56,086 --> 01:20:57,346 to the default folder, 1980 01:20:57,446 --> 01:20:59,706 the default root folder of this application. 1981 01:21:00,226 --> 01:21:04,236 Then give me specifically the path for the following resource: 1982 01:21:04,236 --> 01:21:06,296 "small,", and what data type is it? 1983 01:21:06,526 --> 01:21:09,056 P list. So this is a way of telling iOS, 1984 01:21:09,356 --> 01:21:11,406 give me a file called P List, sorry, 1985 01:21:11,406 --> 01:21:13,536 give me a file called small dot something. 1986 01:21:13,926 --> 01:21:16,256 That something is P List because it's of type P List, 1987 01:21:16,256 --> 01:21:18,356 and this helps it know how to load the file, 1988 01:21:18,356 --> 01:21:20,576 whether it's a Property List, a binary file, 1989 01:21:20,576 --> 01:21:21,796 or some generic text file. 1990 01:21:22,226 --> 01:21:23,646 Then I'm out doing this. 1991 01:21:23,746 --> 01:21:26,906 On the left-hand side, what's going on here 1992 01:21:26,906 --> 01:21:28,086 in this highlighted portion? 1993 01:21:28,086 --> 01:21:29,126 >> [Inaudible audience response]. 1994 01:21:29,126 --> 01:21:34,976 >> Good. I'm creating a pointer to an NS Array Object, 1995 01:21:34,976 --> 01:21:39,546 and on the right-hand side, I'm calling NS Array Alloc In It 1996 01:21:39,546 --> 01:21:41,106 With Contents Of File. 1997 01:21:41,346 --> 01:21:43,296 So there's a bunch of different ways to do this. 1998 01:21:43,426 --> 01:21:46,926 I have chosen to use NS Arrays Alloc method, and then the 1999 01:21:46,926 --> 01:21:49,706 In It Method, called In Its With Contents Of File, and it turns 2000 01:21:49,706 --> 01:21:51,646 out that if I read the documentation for that method, 2001 01:21:51,646 --> 01:21:55,126 it just knows how to load that information into the file. 2002 01:21:55,826 --> 01:21:58,476 But I thought NS Arrays were unmutable? 2003 01:21:59,516 --> 01:22:00,206 Were immutable? 2004 01:22:00,776 --> 01:22:04,626 In other words, I thought you couldn't change them, 2005 01:22:05,226 --> 01:22:08,496 but I'm clearly initializing this one with words. 2006 01:22:09,146 --> 01:22:11,616 How do we reconcile that? 2007 01:22:11,616 --> 01:22:11,826 What's that? 2008 01:22:11,886 --> 01:22:14,156 >> You never allocated or initialized it. 2009 01:22:14,386 --> 01:22:18,796 >> I never allocated it or initialized it, 2010 01:22:18,796 --> 01:22:21,646 but I did allocate and initialize it here, right? 2011 01:22:21,646 --> 01:22:23,526 >> Not on both sides. 2012 01:22:23,666 --> 01:22:25,206 >> You haven't changed the arrays 2013 01:22:25,206 --> 01:22:27,496 and you just have it typed NS Array pointer. 2014 01:22:27,656 --> 01:22:29,946 >> So that's okay, on the left-hand side. 2015 01:22:30,526 --> 01:22:32,386 But why is this not a mutable array? 2016 01:22:32,496 --> 01:22:35,576 I'm adding stuff to it which means I'm changing it, right? 2017 01:22:35,576 --> 01:22:37,066 >> [Inaudible audience response]. 2018 01:22:37,066 --> 01:22:40,386 >> Yes, that's the key distinction. 2019 01:22:40,386 --> 01:22:42,986 If you could never mutate arrays, 2020 01:22:42,986 --> 01:22:45,676 you could never have anything in an NS Array. 2021 01:22:45,676 --> 01:22:46,926 It would be a useless object. 2022 01:22:47,206 --> 01:22:50,346 But in this case, we have an NS Array that's being initialized 2023 01:22:50,776 --> 01:22:53,816 at the point of allocation with the contents of a file, 2024 01:22:53,816 --> 01:22:55,986 so the fact that it's an NS Array just means I can't change 2025 01:22:55,986 --> 01:22:58,496 it after this line of code. 2026 01:22:58,626 --> 01:23:00,996 And that makes sense, because if this application is just going 2027 01:23:00,996 --> 01:23:03,426 to show this list of words, much like Evil Hangman is going 2028 01:23:03,426 --> 01:23:05,866 to have a long list of words in its memory, 2029 01:23:06,186 --> 01:23:07,486 you're not going to want to change it. 2030 01:23:07,486 --> 01:23:09,596 You just want to have one copy of that lying around, 2031 01:23:09,596 --> 01:23:11,076 and it's slightly more efficient 2032 01:23:11,326 --> 01:23:14,486 to have the NS Array class instead of the NS Mutable Array, 2033 01:23:14,486 --> 01:23:16,616 because one, there's less functionality, 2034 01:23:16,616 --> 01:23:19,286 there's not the editing code related to it, and two, 2035 01:23:19,286 --> 01:23:20,676 you protect yourself against yourself. 2036 01:23:20,676 --> 01:23:23,096 You can't accidentally delete a word from your dictionary 2037 01:23:23,296 --> 01:23:26,956 if you've said to the compiler, this is an immutable NS Array. 2038 01:23:27,056 --> 01:23:28,176 All right. 2039 01:23:28,176 --> 01:23:31,366 So lastly, I'm just remembering that pointer by assigning it 2040 01:23:31,366 --> 01:23:34,616 to my property called Words, and then I'm returning myself. 2041 01:23:34,616 --> 01:23:38,176 So at this point in the program, I have loaded that Property List 2042 01:23:38,176 --> 01:23:40,626 into memory, stored it in a property, so now I have access 2043 01:23:40,626 --> 01:23:42,316 to an NS Array that I can iterate over 2044 01:23:42,316 --> 01:23:43,256 and do whatever I want. 2045 01:23:43,686 --> 01:23:45,886 So the application now looks like this. 2046 01:23:45,886 --> 01:23:50,566 It's a table of words and I now somehow have to render one, two, 2047 01:23:50,566 --> 01:23:52,996 three, four, five cells, 2048 01:23:53,376 --> 01:23:56,126 but I don't proactively push the cells to the UI. 2049 01:23:56,126 --> 01:24:00,896 I'm instead going to have the -- the iOS is going to ask me, 2050 01:24:00,896 --> 01:24:01,846 what do you want at this cell? 2051 01:24:01,846 --> 01:24:02,806 What do you want at this cell? 2052 01:24:02,806 --> 01:24:03,726 What do you want at this cell? 2053 01:24:03,726 --> 01:24:05,016 Or rather, what do you want at this row? 2054 01:24:05,016 --> 01:24:05,936 This row? This row? 2055 01:24:06,156 --> 01:24:08,146 And I have to return a cell to it. 2056 01:24:08,476 --> 01:24:11,226 So if I go back to the code, notice that we have this thing, 2057 01:24:11,226 --> 01:24:14,786 number of sections in TableView, so that's okay here 2058 01:24:14,786 --> 01:24:16,466 because it's just one big table. 2059 01:24:16,466 --> 01:24:17,856 There's not different groupings. 2060 01:24:18,096 --> 01:24:20,356 As an aside, if I go back here, 2061 01:24:20,356 --> 01:24:22,356 let me see if I can show you the opposite. 2062 01:24:22,356 --> 01:24:26,436 If I go into settings, this is a UITableView, so if you go 2063 01:24:26,436 --> 01:24:29,806 into an iOS device, you've seen to UITableView's for years now. 2064 01:24:30,156 --> 01:24:33,396 Those -- this is a UITableView with one, two, three, 2065 01:24:33,396 --> 01:24:35,656 at least four sections, each 2066 01:24:35,656 --> 01:24:37,996 of which has some non-zero number of rows. 2067 01:24:38,146 --> 01:24:39,546 So that's all we mean by sections. 2068 01:24:39,836 --> 01:24:40,896 But the game we're playing, 2069 01:24:40,896 --> 01:24:44,156 or the program we're using here just as one such section 2070 01:24:44,156 --> 01:24:45,326 since we don't see the gray. 2071 01:24:45,656 --> 01:24:46,496 So what next? 2072 01:24:46,496 --> 01:24:49,236 This, actually let me delete for simplicity 2073 01:24:49,546 --> 01:24:53,576 since it's not necessary here, and now we have TableView, 2074 01:24:53,626 --> 01:24:55,146 Self or Row At Index Path. 2075 01:24:55,616 --> 01:24:56,656 When is this method called? 2076 01:25:03,436 --> 01:25:05,476 When or why is this method called? 2077 01:25:05,986 --> 01:25:06,986 What's that? 2078 01:25:06,986 --> 01:25:07,186 >> [Inaudible audience response]. 2079 01:25:07,186 --> 01:25:15,516 >> When you try to get a cell and you pass in the Index Path, 2080 01:25:15,516 --> 01:25:18,956 yes, so this is really -- the operating system is going 2081 01:25:18,956 --> 01:25:21,796 to call this method or more specifically, the Controller, 2082 01:25:21,996 --> 01:25:25,996 is going to call this method, or rather the View is going 2083 01:25:25,996 --> 01:25:28,946 to call this method When I Want To Render A Cell On The Screen, 2084 01:25:28,946 --> 01:25:31,696 it's going to say what belongs at section zero, row zero. 2085 01:25:31,696 --> 01:25:34,746 What belongs at section zero, row one, row two, row three, 2086 01:25:34,836 --> 01:25:38,076 and my job, as we saw earlier with Master Detail, is to return 2087 01:25:38,076 --> 01:25:40,366 to this thing an object representing that row 2088 01:25:40,366 --> 01:25:42,066 in the table with whatever text I want, 2089 01:25:42,246 --> 01:25:43,646 whatever buttons I want inside. 2090 01:25:43,646 --> 01:25:46,716 So we have this same trick using the reusable cells. 2091 01:25:47,066 --> 01:25:49,006 I'm using "cell" again this time. 2092 01:25:49,636 --> 01:25:53,346 If not, I instantiated as needed and then down here, 2093 01:25:53,486 --> 01:25:55,396 I am initializing the cell as follows. 2094 01:25:55,396 --> 01:25:58,296 One, I'm setting it so-called selection style 2095 01:25:58,576 --> 01:26:02,206 to be UITableView Cell Selection Style None. 2096 01:26:02,506 --> 01:26:03,326 What does that mean? 2097 01:26:03,576 --> 01:26:05,636 It just means that when the user's finger clicks 2098 01:26:05,636 --> 01:26:06,996 on this TableView, like I'm doing 2099 01:26:06,996 --> 01:26:08,976 with my mouse, nothing happens. 2100 01:26:08,976 --> 01:26:10,696 It doesn't become blue, it doesn't get selected. 2101 01:26:10,936 --> 01:26:12,826 >> So UITableView is getting rows [inaudible]? 2102 01:26:13,036 --> 01:26:13,226 >> Correct. 2103 01:26:14,216 --> 01:26:16,096 It's asking me what do you want here. 2104 01:26:16,096 --> 01:26:16,896 What do you want here? 2105 01:26:16,896 --> 01:26:17,876 What do you want here? 2106 01:26:17,876 --> 01:26:20,806 And I have to hand it back the rectangular cell effectively. 2107 01:26:20,896 --> 01:26:25,206 Exactly. And then I'm setting the cells text labels text equal 2108 01:26:25,206 --> 01:26:29,596 to be whatever is returned from the object at index row, 2109 01:26:29,596 --> 01:26:31,826 so what's at index zero, what's at index one, 2110 01:26:31,886 --> 01:26:34,356 and then I'm passing that message to words 2111 01:26:34,666 --> 01:26:37,846 so that I get the zero object, the one object, 2112 01:26:37,846 --> 01:26:39,646 two object, three, and so forth. 2113 01:26:39,826 --> 01:26:46,326 And if I change this, for instance, to that, semicolon, 2114 01:26:46,476 --> 01:26:49,436 and rerun the application, what I should get, 2115 01:26:49,436 --> 01:26:51,296 despite all of that effort to store data, 2116 01:26:51,556 --> 01:26:54,456 is just the same string again and again and again. 2117 01:26:54,456 --> 01:26:57,776 So that's truly a method that's being called. 2118 01:26:58,206 --> 01:27:00,226 Finally down here, this one's different. 2119 01:27:00,486 --> 01:27:03,316 Number -- TableView number of rows in section, 2120 01:27:03,386 --> 01:27:05,476 this is the method that I'm going -- 2121 01:27:05,476 --> 01:27:06,406 that's going to be invoked 2122 01:27:06,406 --> 01:27:08,696 when asked how many rows the section zero have 2123 01:27:08,696 --> 01:27:11,946 so that iOS knows how many times to ask you for the cells. 2124 01:27:12,206 --> 01:27:14,256 In this case, I have not hardcoded a value 2125 01:27:14,446 --> 01:27:16,746 because I don't remember how many words are 2126 01:27:16,746 --> 01:27:18,516 in the Property List, and maybe it would even change 2127 01:27:18,516 --> 01:27:19,216 with an update. 2128 01:27:19,486 --> 01:27:22,026 So we pass in the Count Message to Self.Words, 2129 01:27:22,026 --> 01:27:24,516 which gives me the array's length. 2130 01:27:25,526 --> 01:27:25,686 Yes. 2131 01:27:26,816 --> 01:27:31,296 >> So in case where you're passing through a file, 2132 01:27:31,376 --> 01:27:35,776 we have an array that's not immutable. 2133 01:27:35,776 --> 01:27:40,026 You're editing the actual file itself, I'm sorry, 2134 01:27:40,026 --> 01:27:43,316 the P List itself in your-- ? 2135 01:27:43,886 --> 01:27:46,156 >> No editing has happened to the P list here. 2136 01:27:46,156 --> 01:27:48,466 >> No, but I'm saying in terms of like if you wanted to -- 2137 01:27:48,596 --> 01:27:52,696 if the P List had like more contents, 2138 01:27:52,866 --> 01:27:54,616 this would already account. 2139 01:27:55,056 --> 01:27:55,586 >> Yes. 2140 01:27:55,586 --> 01:27:55,816 >> Okay. 2141 01:27:55,916 --> 01:27:56,346 >> Exactly. 2142 01:27:56,346 --> 01:27:58,996 This is good design, because even though I could go 2143 01:27:58,996 --> 01:28:01,416 to the application and I could do a one, two, three, four, 2144 01:28:01,416 --> 01:28:04,886 there's five words in my P list, I could just write return five. 2145 01:28:05,176 --> 01:28:08,446 The catch is that whereas it's reasonable to assume 2146 01:28:08,446 --> 01:28:11,616 that my UI has zero, has one section forever, 2147 01:28:11,616 --> 01:28:13,986 because that's how I designed the user experience to be, 2148 01:28:13,986 --> 01:28:16,216 with just one big TableView, no notion of sections, 2149 01:28:16,606 --> 01:28:19,866 that in theory could change, and it's a poor design decision if, 2150 01:28:20,106 --> 01:28:22,506 not only do I have to update the Property List in a year 2151 01:28:22,506 --> 01:28:25,006 when I ship a new version with ten words and not five, 2152 01:28:25,326 --> 01:28:26,716 but to also have to change it there. 2153 01:28:26,716 --> 01:28:28,916 It's just inviting bugs and unmaintainability. 2154 01:28:29,816 --> 01:28:31,636 So that's all. 2155 01:28:31,856 --> 01:28:32,636 All right. 2156 01:28:32,636 --> 01:28:36,556 So nice and sexier maybe, but let's actually do something 2157 01:28:36,556 --> 01:28:39,236 where we interact with the glass of the screen and do something 2158 01:28:39,236 --> 01:28:42,076 like clicking or dragging or pinching, and see how we can add 2159 01:28:42,116 --> 01:28:43,266 that element, particularly 2160 01:28:43,266 --> 01:28:45,096 as you contemplate what you might want to do 2161 01:28:45,096 --> 01:28:47,086 with your third and final project. 2162 01:28:47,086 --> 01:28:51,026 So it turns out that iOS supports a whole bunch 2163 01:28:51,026 --> 01:28:53,836 of gestures, and you're probably familiar with these naturally 2164 01:28:53,836 --> 01:28:56,356 if you have a device like this, but they all reduce 2165 01:28:56,356 --> 01:28:58,106 to some key class name. 2166 01:28:58,106 --> 01:29:01,196 So we have things like UITapGestureRecognizer. 2167 01:29:01,466 --> 01:29:03,596 This is the type of object that if you instantiate, 2168 01:29:03,766 --> 01:29:06,986 you have the ability to detect that on an arbitrary portion 2169 01:29:06,986 --> 01:29:09,716 onto the screen, not necessarily right on top of a button, 2170 01:29:09,776 --> 01:29:11,306 which is handled for you automatically. 2171 01:29:11,626 --> 01:29:14,296 Pinch, which is doing something like this often to zoom. 2172 01:29:14,516 --> 01:29:17,136 Rotations, kind of twisting your fingers around, 2173 01:29:17,136 --> 01:29:18,756 swiping left to right, up to down. 2174 01:29:19,066 --> 01:29:21,686 Pan gesture, if you want to move something across the screen 2175 01:29:21,686 --> 01:29:24,576 and long press, if you want to click and hold for like a second 2176 01:29:24,576 --> 01:29:27,066 or two, that, too, can be detected differently. 2177 01:29:27,066 --> 01:29:29,236 And if you've used Google maps or Apple Maps or the like, 2178 01:29:29,236 --> 01:29:32,096 you've experienced a bunch of the different UI mechanisms. 2179 01:29:32,366 --> 01:29:34,186 So how do we start doing that? 2180 01:29:34,656 --> 01:29:39,086 Well, let me go into some code in our last project here 2181 01:29:39,086 --> 01:29:44,806 for the evening and open up the one called Gestures. 2182 01:29:45,256 --> 01:29:47,736 Now in advance, I went on Facebook 2183 01:29:48,236 --> 01:29:50,136 and downloaded a few photographs. 2184 01:29:50,876 --> 01:29:53,686 Let me go ahead and run this application, 2185 01:29:54,636 --> 01:29:56,276 and we have this application here. 2186 01:29:57,046 --> 01:30:02,686 And if we swipe to the right, there's his graduation. 2187 01:30:03,006 --> 01:30:06,456 And one more, in his plumbers outfit from this weekend. 2188 01:30:06,876 --> 01:30:10,336 So we can keep flipping through this, and each time I swipe 2189 01:30:10,336 --> 01:30:12,816 from right to left, even though you can just barely see my 2190 01:30:12,816 --> 01:30:15,116 mouse, it's like I'm sliding my finger from left to right. 2191 01:30:15,116 --> 01:30:15,956 And I kept it simple. 2192 01:30:15,956 --> 01:30:18,326 I didn't do it quite so that he's sliding off the screen. 2193 01:30:18,596 --> 01:30:21,296 As soon as I start sliding, it just jumps off to the side, 2194 01:30:21,296 --> 01:30:22,156 just to keep it simple. 2195 01:30:22,336 --> 01:30:24,376 But also, if I click and hold on, like, his nose, 2196 01:30:24,376 --> 01:30:27,326 it's going to nag at me because I'm using a long press 2197 01:30:27,636 --> 01:30:28,666 gesture recognizer. 2198 01:30:28,666 --> 01:30:30,466 So how do we go about implementing this 2199 01:30:30,696 --> 01:30:33,356 and implementing that kind of functionality? 2200 01:30:33,506 --> 01:30:34,506 Well, let's go into this. 2201 01:30:34,506 --> 01:30:37,496 So in my project here, I've got some familiar files 2202 01:30:37,496 --> 01:30:38,166 and some new ones. 2203 01:30:38,166 --> 01:30:40,526 Under supporting files, I have three photos of Rob, 2204 01:30:40,766 --> 01:30:43,596 so these are just JPEGs that I dragged and dropped 2205 01:30:43,596 --> 01:30:45,816 after renaming them, after downloading them from Facebook. 2206 01:30:45,816 --> 01:30:47,496 I encourage you to friend Rob on Facebook. 2207 01:30:47,496 --> 01:30:49,966 If you then drag them into the project, 2208 01:30:49,966 --> 01:30:52,106 I can now access them programmatically. 2209 01:30:52,106 --> 01:30:55,216 And so now, I can do something like this. 2210 01:30:55,596 --> 01:30:57,796 In Main.M is some usual code. 2211 01:30:58,376 --> 01:31:01,566 In AppDelegate.H, is some usual code. 2212 01:31:01,966 --> 01:31:04,726 In AppDelegate.M is some usual code. 2213 01:31:04,726 --> 01:31:05,696 So nothing new here. 2214 01:31:05,696 --> 01:31:07,666 We're building on the same principles as before, 2215 01:31:07,856 --> 01:31:09,946 so the magic must be somewhere in my Nib 2216 01:31:09,946 --> 01:31:11,236 in my ViewController files. 2217 01:31:11,576 --> 01:31:15,196 So my ViewController.Nib file also looks very simple. 2218 01:31:15,506 --> 01:31:19,446 I dragged and dropped a class called UIImageView, 2219 01:31:19,446 --> 01:31:22,976 which is like a video player, but for images. 2220 01:31:22,976 --> 01:31:26,216 It's just a placeholder for single PNG or gif or JPEG 2221 01:31:26,216 --> 01:31:29,556 or the like, and I configured it to just fill the whole screen. 2222 01:31:30,006 --> 01:31:32,266 So I need to somehow programmatically have access 2223 01:31:32,266 --> 01:31:32,726 to that. 2224 01:31:32,956 --> 01:31:35,416 So a good place to start, again, when downloading code 2225 01:31:35,416 --> 01:31:39,086 that someone else wrote or that you download online as part 2226 01:31:39,086 --> 01:31:41,496 of a bigger project, is just control click on it, 2227 01:31:41,646 --> 01:31:46,916 and it looks like there is a ImageView Property somewhere 2228 01:31:46,916 --> 01:31:49,256 that's pointing to file's owner. 2229 01:31:49,256 --> 01:31:51,316 So there's some kind of linkage happening here, 2230 01:31:51,316 --> 01:31:53,126 some kind of outlet to the files owner. 2231 01:31:53,436 --> 01:31:59,056 So let's look at my.H file, and if I go into my.H file, 2232 01:31:59,576 --> 01:32:01,276 nothing there, that's interesting. 2233 01:32:01,276 --> 01:32:04,376 ViewController.M, so I've tried 2234 01:32:04,376 --> 01:32:06,206 to take things one step further here. 2235 01:32:06,206 --> 01:32:08,196 Thus far, we've been putting properties 2236 01:32:08,196 --> 01:32:10,986 and method declarations in our .H files, 2237 01:32:11,366 --> 01:32:14,406 which is a common convention, but it's not strictly necessary, 2238 01:32:14,406 --> 01:32:18,576 because if all of my methods are implemented in this same file, 2239 01:32:18,916 --> 01:32:22,196 and if no one else is going to be importing my.H file, 2240 01:32:22,196 --> 01:32:24,476 and they probably shouldn't be importing my ViewController. 2241 01:32:24,476 --> 01:32:27,346 You would typically import utility classes, 2242 01:32:27,346 --> 01:32:32,176 or files with constants, or files for models and the like, 2243 01:32:32,366 --> 01:32:34,766 there's really no reason for me to advertise to the world 2244 01:32:34,766 --> 01:32:37,676 in principle in my.H file all of this internal functionality. 2245 01:32:37,966 --> 01:32:41,406 So I can certainly just declare these properties as private 2246 01:32:41,716 --> 01:32:44,336 by putting them in this file, and I say private typically 2247 01:32:44,336 --> 01:32:46,686 because again, you can still send messages to objects. 2248 01:32:46,686 --> 01:32:48,926 They may very well respond, but just in the interest 2249 01:32:48,926 --> 01:32:50,696 of not advertising features, 2250 01:32:50,696 --> 01:32:53,326 much like Apple does not advertise certain APIs, 2251 01:32:53,326 --> 01:32:55,326 they keep them private though people figure it out, 2252 01:32:55,626 --> 01:32:58,216 I've decided to declare all of my properties here 2253 01:32:58,216 --> 01:33:02,556 in this file my.M. So I seem to have a few properties. 2254 01:33:02,556 --> 01:33:04,966 One is a bullion called Alert In Progress, 2255 01:33:05,466 --> 01:33:06,846 and I ended up using that. 2256 01:33:06,846 --> 01:33:08,966 If I fast forward to the end of the story, because I needed 2257 01:33:08,966 --> 01:33:12,846 to remember if and when I had touched Rob's face for too long 2258 01:33:12,846 --> 01:33:15,236 and therefore trigger the AlertView, because I ran 2259 01:33:15,236 --> 01:33:17,656 into a bug through trial and error that if I kept holding, 2260 01:33:17,656 --> 01:33:19,996 I might get multiple AlertViews, and I didn't want to do that. 2261 01:33:19,996 --> 01:33:21,976 So I wanted a simple locking mechanism 2262 01:33:22,186 --> 01:33:25,416 to make sure I only open one AlertView ever. 2263 01:33:25,746 --> 01:33:29,946 So next I have an ImageView pointer to a UIImageView, 2264 01:33:29,946 --> 01:33:32,126 and that's my IBOutlet, so that's the wiring 2265 01:33:32,126 --> 01:33:33,826 between that IDImageView -- 2266 01:33:33,826 --> 01:33:36,496 sorry, that UIImageView and my code. 2267 01:33:36,796 --> 01:33:38,396 Then I have an index. 2268 01:33:38,396 --> 01:33:39,486 I'm not sure what that is. 2269 01:33:39,486 --> 01:33:41,236 And then I have some Robs in the form 2270 01:33:41,236 --> 01:33:42,536 of a pointer to an NS Array. 2271 01:33:42,536 --> 01:33:44,526 So let's take a guess. 2272 01:33:44,526 --> 01:33:46,706 What is going to go in that NS Array probably? 2273 01:33:46,706 --> 01:33:46,826 Yeah. 2274 01:33:47,496 --> 01:33:48,636 >> The images? 2275 01:33:48,726 --> 01:33:49,436 >> The images. 2276 01:33:49,436 --> 01:33:52,146 So specifically maybe the names of the images that we'll see 2277 01:33:52,146 --> 01:33:54,576 in just a moment, and then the [inaudible] it's called index? 2278 01:33:55,236 --> 01:33:56,356 >> Where you are. 2279 01:33:56,356 --> 01:33:57,196 >> Where I am. 2280 01:33:57,196 --> 01:33:59,566 So I realize again by thinking through the design of this, 2281 01:33:59,566 --> 01:34:02,816 if I want to implement this -- this sort of carousel of Robs 2282 01:34:02,816 --> 01:34:05,356 and I want it to wrap around so that the third image goes back 2283 01:34:05,356 --> 01:34:07,056 to the first image, I decided just 2284 01:34:07,056 --> 01:34:10,566 to use an index that's going to be a 012, 012, 2285 01:34:10,566 --> 01:34:12,706 and I can use some modular arithmetic to wrap around, 2286 01:34:12,706 --> 01:34:14,796 like you might've done in other languages. 2287 01:34:15,106 --> 01:34:16,636 So that's where this is going. 2288 01:34:16,836 --> 01:34:19,366 Meanwhile, I've got some private methods, private only 2289 01:34:19,366 --> 01:34:21,646 in the sense that they're not advertised in my.H, 2290 01:34:21,906 --> 01:34:25,006 called you -- Alert View Did Dismiss With Button Index. 2291 01:34:25,416 --> 01:34:26,426 We've seen that before. 2292 01:34:26,426 --> 01:34:27,586 When is that method called? 2293 01:34:28,196 --> 01:34:29,376 Think back to last week. 2294 01:34:29,376 --> 01:34:29,826 >> [Inaudible audience response]. 2295 01:34:29,826 --> 01:34:33,456 >> When the user clicks the cancellation button, 2296 01:34:33,456 --> 01:34:35,396 however labeled, that big default button. 2297 01:34:35,656 --> 01:34:38,686 I now have another method called Handle Long Press, 2298 01:34:38,686 --> 01:34:42,186 and the Handle Swipe, and those are implemented 2299 01:34:42,186 --> 01:34:45,846 to receive something called a Recognizer, so a pointer 2300 01:34:45,846 --> 01:34:48,666 to some kind of logic that has recognized what the user has 2301 01:34:48,666 --> 01:34:50,706 done so I can glean some information about it. 2302 01:34:51,066 --> 01:34:55,156 So now if I scroll down, what am I going to do when -- 2303 01:34:55,526 --> 01:34:58,496 let's do the Handle Long Press, because it's a little simpler. 2304 01:34:58,796 --> 01:35:00,896 So when I click and hold on Rob's nose, 2305 01:35:00,896 --> 01:35:02,636 or frankly anywhere on the image. 2306 01:35:02,636 --> 01:35:04,796 It doesn't matter based on how I've implemented this, 2307 01:35:05,156 --> 01:35:06,416 what is going to happen? 2308 01:35:06,416 --> 01:35:10,776 Well, iOS is going to recognize that you're holding Rob's face 2309 01:35:10,776 --> 01:35:13,206 down for quite some time, and therefore some code's going 2310 01:35:13,206 --> 01:35:15,796 to get executed, specifically this method, Handle Long Press. 2311 01:35:15,796 --> 01:35:18,386 I'm going to be passed a pointer to the recognizer, 2312 01:35:18,386 --> 01:35:20,706 in case that's useful, and what I decided to do 2313 01:35:20,706 --> 01:35:22,606 with that information here is what you saw. 2314 01:35:22,826 --> 01:35:24,606 I'm going to first check, wait a minute, 2315 01:35:24,606 --> 01:35:26,066 is there already alert in progress? 2316 01:35:26,256 --> 01:35:28,166 This is the bull that I referred to earlier, 2317 01:35:28,166 --> 01:35:30,036 just to make sure we don't get stuck in an infinite loop 2318 01:35:30,036 --> 01:35:32,576 by holding his face for four seconds instead of just two. 2319 01:35:33,106 --> 01:35:35,726 Then I set it to yes, so that I remember, 2320 01:35:35,726 --> 01:35:37,506 and this is single threaded code at this point, 2321 01:35:37,506 --> 01:35:40,316 so it's not a problem if I'm still holding down. 2322 01:35:40,746 --> 01:35:43,406 Then I'm going to go ahead and allocate a UIAlertView, 2323 01:35:43,406 --> 01:35:44,716 and we saw this code last time, 2324 01:35:44,716 --> 01:35:46,046 even though the words are now different. 2325 01:35:46,046 --> 01:35:47,866 It's going to say, hey, stop that. 2326 01:35:48,216 --> 01:35:52,356 I have a delegate of self, so not nil, and a cancel button 2327 01:35:52,446 --> 01:36:01,736 of fine, so this delegate of self is used for what purpose? 2328 01:36:01,736 --> 01:36:01,866 >> [Inaudible audience response]. 2329 01:36:01,866 --> 01:36:05,406 >> To tell the ViewController that it is done, 2330 01:36:05,406 --> 01:36:07,166 that the user has dismissed it specifically. 2331 01:36:07,166 --> 01:36:08,586 So not the View, the ViewController, 2332 01:36:08,876 --> 01:36:11,346 and that is what invokes this method, recall, 2333 01:36:11,506 --> 01:36:14,116 which we said a moment ago is the method that's called 2334 01:36:14,116 --> 01:36:17,266 when you click that close button on a UIAlertView. 2335 01:36:17,266 --> 01:36:19,776 So all of that stuff is pretty much identical 2336 01:36:19,776 --> 01:36:20,886 to what we saw last week. 2337 01:36:21,146 --> 01:36:24,326 So that's the method that's called When I Do A Long Press, 2338 01:36:24,326 --> 01:36:27,076 but how did I teach the program to even listen 2339 01:36:27,276 --> 01:36:30,286 for those long presses on the image in question? 2340 01:36:30,286 --> 01:36:33,736 Well, if I scroll down, we look to a couple of places here. 2341 01:36:34,016 --> 01:36:35,546 One is In It With Nib Name. 2342 01:36:35,836 --> 01:36:36,886 So this again is going to be 2343 01:36:36,886 --> 01:36:39,836 that method that's automatically called when you are using -- 2344 01:36:39,836 --> 01:36:41,816 when you are using Nibs in your program. 2345 01:36:42,216 --> 01:36:44,866 This is the opposite of using Storyboards, for instance, 2346 01:36:44,866 --> 01:36:46,546 but there's a similar mechanism for those. 2347 01:36:46,796 --> 01:36:50,386 So In It With Nib Name is copy and paste it essentially 2348 01:36:50,386 --> 01:36:52,936 from before, but I've added a bit of code in the middle. 2349 01:36:53,226 --> 01:36:56,546 I first said Alert In Progress, no, 2350 01:36:56,546 --> 01:36:58,136 because I want to know by default. 2351 01:36:58,316 --> 01:37:00,036 There is no long press, and that makes sense. 2352 01:37:00,036 --> 01:37:02,106 When the program starts, no one's touching it by default. 2353 01:37:02,106 --> 01:37:05,326 And then I prepare the Rob, so to speak, and that's one way 2354 01:37:05,326 --> 01:37:06,436 to initialize the array. 2355 01:37:06,926 --> 01:37:10,316 I Alloc an NS Array, In It With Objects, 2356 01:37:10,436 --> 01:37:13,286 and if I am not loading it from a file, for instance, 2357 01:37:13,286 --> 01:37:17,136 just from a comma separated list, the syntax is string, 2358 01:37:17,406 --> 01:37:21,186 string, string, nil, all in square brackets. 2359 01:37:21,316 --> 01:37:24,916 So that much like C is how you can declare an array statically. 2360 01:37:25,126 --> 01:37:26,346 The nil is important. 2361 01:37:26,346 --> 01:37:28,676 You have to terminate the cease-file array 2362 01:37:28,676 --> 01:37:29,416 for that reason. 2363 01:37:29,756 --> 01:37:33,526 On then Self.Index Gets Zero, what does this mean? 2364 01:37:34,666 --> 01:37:35,176 What's the -- ? 2365 01:37:35,346 --> 01:37:36,736 >> Start at the zero. 2366 01:37:36,736 --> 01:37:39,556 >> Yeah, start with the first Rob at index location zero. 2367 01:37:39,876 --> 01:37:42,266 So next, View Did Load, recall, 2368 01:37:42,266 --> 01:37:45,176 is the method that's called once your View, 2369 01:37:45,226 --> 01:37:48,156 your user interface has been loaded, and this is your point 2370 01:37:48,156 --> 01:37:51,536 at which to start configuring some last-minute details, 2371 01:37:51,536 --> 01:37:52,866 after everything's been opened 2372 01:37:52,866 --> 01:37:54,446 up from the Nib file, for instance. 2373 01:37:54,656 --> 01:37:57,396 So this is new code, but hopefully pretty readable. 2374 01:37:57,716 --> 01:38:00,976 So notice I first call the parent class's version of this. 2375 01:38:00,976 --> 01:38:04,076 Woops, the parent class, so I call Super View Did Load, 2376 01:38:04,376 --> 01:38:05,646 then I load the image. 2377 01:38:05,806 --> 01:38:08,966 So Self.Image View.Image. 2378 01:38:09,956 --> 01:38:11,226 Self.Image View is what? 2379 01:38:11,866 --> 01:38:13,316 >> A property. 2380 01:38:13,366 --> 01:38:15,856 >> It's a property of type UIImageView. 2381 01:38:15,856 --> 01:38:18,066 If I read the documentation for UIImageView, 2382 01:38:18,066 --> 01:38:22,266 turns out that a UIImageView has a property called image whose 2383 01:38:22,266 --> 01:38:25,176 value is a pointer to a... 2384 01:38:25,756 --> 01:38:25,876 >> UI. 2385 01:38:26,076 --> 01:38:27,926 >> UIImageObject, apparently. 2386 01:38:27,926 --> 01:38:30,086 We've not seen this before, but you can now it reader 2387 01:38:30,086 --> 01:38:31,906 from the code itself, so this -- 2388 01:38:32,266 --> 01:38:34,356 this class here is called UIImage. 2389 01:38:34,636 --> 01:38:38,696 Turns out it has a Convenience Method called image name whereby 2390 01:38:38,736 --> 01:38:42,576 if I get the I'th Rob at the current index, 2391 01:38:42,576 --> 01:38:45,486 so give me Rob's bracket zero, but do it dynamically 2392 01:38:45,486 --> 01:38:48,616 in code here, that is going to give me an Image Object, 2393 01:38:48,616 --> 01:38:52,116 UI image with Rob, and I'm going to plop it into the carousel, 2394 01:38:52,116 --> 01:38:54,116 essentially, the UIImageView that allows me 2395 01:38:54,116 --> 01:38:56,456 to show the image to someone. 2396 01:38:57,156 --> 01:39:00,316 So now I'm going to listen for presses on Rob's image. 2397 01:39:00,566 --> 01:39:02,046 So code's a little ugly, 2398 01:39:02,046 --> 01:39:04,686 but what I'm doing is declaring a pointer called Long Press 2399 01:39:04,686 --> 01:39:07,676 Gesture of type UI Long Press Gesture Recognizer. 2400 01:39:08,146 --> 01:39:09,736 I am assigning it the return value 2401 01:39:09,736 --> 01:39:12,776 of calling UI Long Press Gesture Recognizer Ella, 2402 01:39:12,996 --> 01:39:14,506 so just give me one of these recognizers. 2403 01:39:14,996 --> 01:39:16,816 I'm initializing it with a target. 2404 01:39:17,326 --> 01:39:19,106 Self, we'll come back to than a second. 2405 01:39:19,366 --> 01:39:21,656 Action called Handle Long Press. 2406 01:39:22,356 --> 01:39:27,886 So in layman's terms, this is listening for a long press, 2407 01:39:28,606 --> 01:39:30,366 but in slightly more technical terms, 2408 01:39:30,406 --> 01:39:35,196 what are we telling the UI long press gesture recognizer object 2409 01:39:35,296 --> 01:39:37,786 exactly with in it with target and action here? 2410 01:39:37,836 --> 01:39:47,226 >> First you're saying that the message to be sent 2411 01:39:47,226 --> 01:39:50,846 when the long press happens is Handle Long Press. 2412 01:39:50,876 --> 01:39:50,966 >> Good. 2413 01:39:50,996 --> 01:39:52,166 >> And you're also saying you should send that message 2414 01:39:52,196 --> 01:39:52,976 to self, so the View Controller. 2415 01:39:53,266 --> 01:39:53,886 >> Exactly. 2416 01:39:53,886 --> 01:39:59,306 So this, again to recap, means when you detect a UI long press, 2417 01:39:59,306 --> 01:40:01,316 a couple seconds down with your finger, 2418 01:40:01,556 --> 01:40:03,426 send the message Handle Long Press, 2419 01:40:03,426 --> 01:40:04,456 which could've been named anything. 2420 01:40:04,456 --> 01:40:08,726 I came up with that method, but pass it to specifically myself, 2421 01:40:08,916 --> 01:40:10,136 the same ViewController. 2422 01:40:10,286 --> 01:40:11,976 And that's why the method earlier 2423 01:40:11,976 --> 01:40:16,246 in the file is indeed invoked when we hold down the -- 2424 01:40:16,246 --> 01:40:23,056 when we hold down ones finger and call Handle Long Press. 2425 01:40:23,396 --> 01:40:26,496 So the other recognizers, let's see first before we see them 2426 01:40:26,496 --> 01:40:29,406 in action one last time, listen for right swipe. 2427 01:40:29,696 --> 01:40:30,546 So how do I do this? 2428 01:40:30,896 --> 01:40:31,376 Same idea. 2429 01:40:31,516 --> 01:40:34,626 I allocated UI Swipe Gesture Recognizer. 2430 01:40:34,796 --> 01:40:36,286 I initialize it with Target Self, 2431 01:40:36,456 --> 01:40:38,706 and this time I tell it Call Handle Swipe 2432 01:40:39,056 --> 01:40:41,166 when the user swipes from a certain direction. 2433 01:40:41,166 --> 01:40:42,536 But what direction is that? 2434 01:40:42,536 --> 01:40:44,806 In this case, I have to do one additional step. 2435 01:40:44,806 --> 01:40:47,396 I have to specify the direction, and according 2436 01:40:47,396 --> 01:40:48,506 to the documentation, 2437 01:40:48,506 --> 01:40:51,236 swipe gestures have a direction property 2438 01:40:51,416 --> 01:40:54,506 and this crazy long constant is what specifies. 2439 01:40:54,506 --> 01:40:56,936 When I go from right to left, 2440 01:40:57,006 --> 01:40:59,856 essentially this is what should actually happen. 2441 01:40:59,856 --> 01:41:00,536 What should happen? 2442 01:41:00,766 --> 01:41:04,176 Well, here is how we add to an ImageView, 2443 01:41:04,176 --> 01:41:06,596 just like we did a few lines ago for the long press, 2444 01:41:06,966 --> 01:41:11,106 this is how we add a recognizer to an existing view object 2445 01:41:11,436 --> 01:41:13,076 that is on this screen. 2446 01:41:13,146 --> 01:41:15,366 You create this recognizer, and you sort of glue it 2447 01:41:15,366 --> 01:41:16,946 down onto the view so that 2448 01:41:16,946 --> 01:41:19,406 that view triggers these various actions. 2449 01:41:19,806 --> 01:41:20,706 Listen for left swipe. 2450 01:41:21,326 --> 01:41:23,326 I've done that with a separate line of code 2451 01:41:23,326 --> 01:41:25,786 at the end there just by changing the constant 2452 01:41:25,826 --> 01:41:28,146 to be this, and that's so that we can swipe right to left, 2453 01:41:28,556 --> 01:41:31,636 or left to right, to increment or decrement the Robs. 2454 01:41:31,886 --> 01:41:35,956 And if we go back up here, let's look at the code. 2455 01:41:35,956 --> 01:41:38,996 Let me fix this. 2456 01:41:38,996 --> 01:41:40,356 Rob we swapped in this year. 2457 01:41:41,046 --> 01:41:43,566 Handle Swipe works how? 2458 01:41:43,566 --> 01:41:45,436 So this is the method that's called when we swipe right 2459 01:41:45,436 --> 01:41:46,466 to left, left to right. 2460 01:41:46,746 --> 01:41:48,626 This is how we figure out the direction. 2461 01:41:48,916 --> 01:41:51,316 We ask the recognizer that was passed 2462 01:41:51,316 --> 01:41:54,136 in via the sender argument what direction was -- 2463 01:41:54,576 --> 01:41:55,346 were you sent in. 2464 01:41:55,576 --> 01:41:57,496 I'm using a switch, which is like an If Else, 2465 01:41:57,616 --> 01:42:00,196 but just done slightly differently syntactically, 2466 01:42:00,586 --> 01:42:01,636 I decided to do this. 2467 01:42:02,056 --> 01:42:05,646 If the user has swiped up down or down up, do nothing. 2468 01:42:05,886 --> 01:42:08,026 Now technically, these lines of code do nothing useful. 2469 01:42:08,026 --> 01:42:09,916 I just left it there for explicitness sake, 2470 01:42:09,916 --> 01:42:10,916 but it immediately breaks 2471 01:42:10,916 --> 01:42:12,516 which means there's no effect whatsoever. 2472 01:42:12,756 --> 01:42:15,996 Meanwhile the direction left, down here, has to do a bit 2473 01:42:15,996 --> 01:42:18,276 of math, and it took a moment to kind of think about this, 2474 01:42:18,546 --> 01:42:21,416 but I'm updating the index value to be, when I go from right 2475 01:42:21,416 --> 01:42:24,286 to left, plus one, and then I need to wrap 2476 01:42:24,286 --> 01:42:26,276 around with some modular arithmetic based 2477 01:42:26,276 --> 01:42:27,516 on the length of the array. 2478 01:42:27,956 --> 01:42:30,586 Down here meanwhile, if I wanted to wrap 2479 01:42:30,586 --> 01:42:34,536 around to the other direction, I had to effectively subtract 2480 01:42:34,676 --> 01:42:37,396 by one, but I wanted to make sure that we didn't go negative, 2481 01:42:37,446 --> 01:42:39,956 so I also have some addition in there just to make sure 2482 01:42:39,956 --> 01:42:44,086 that two goes to one, one goes to zero, zero goes to two, 2483 01:42:44,086 --> 01:42:45,796 and doesn't accidentally go negative. 2484 01:42:45,796 --> 01:42:48,656 So just some basic modular arithmetic there. 2485 01:42:48,656 --> 01:42:51,456 And then lastly, what actually updates Rob, 2486 01:42:51,456 --> 01:42:55,096 and updates him instantly, is to change the property called Image 2487 01:42:55,096 --> 01:42:59,906 of the ImageView IDOutlets to the image named whatever Rob is 2488 01:42:59,906 --> 01:43:02,136 at that particular index. 2489 01:43:02,716 --> 01:43:04,306 So could have implemented this in different ways. 2490 01:43:04,306 --> 01:43:06,896 Could have stored the actual images in an array as opposed 2491 01:43:06,896 --> 01:43:08,956 to the file names, but we kept it simple in this way 2492 01:43:08,956 --> 01:43:10,976 so that we could actually see the strings explicitly 2493 01:43:10,976 --> 01:43:13,376 in the code, but this is how we can now start listening 2494 01:43:13,376 --> 01:43:15,586 for these things, and any of these kind of interactions, 2495 01:43:15,616 --> 01:43:17,146 pinching and zooming and rotating, 2496 01:43:17,416 --> 01:43:19,986 is implemented similarly by implementing one or more 2497 01:43:19,986 --> 01:43:22,526 of these recognizers, and then responding accordingly. 2498 01:43:23,396 --> 01:43:26,176 >> Is this a handle that we have for competing recognizers, 2499 01:43:26,226 --> 01:43:31,326 say at -- for the long tap, and actually it's a tap 2500 01:43:31,386 --> 01:43:35,456 and it's a long tap because it only triggers long taps? 2501 01:43:35,456 --> 01:43:38,296 >> So in that case, if you're detecting tap versus long tap, 2502 01:43:38,296 --> 01:43:40,926 if you're holding long enough, it will only be a long tap. 2503 01:43:41,096 --> 01:43:43,686 That's what defines it as long, holding it slightly too long. 2504 01:43:43,836 --> 01:43:45,586 If you do it within the window, and I think it's one 2505 01:43:45,586 --> 01:43:46,826 or two seconds, that would be a tap. 2506 01:43:47,546 --> 01:43:49,576 But you won't get both of you're holding down like that. 2507 01:43:49,666 --> 01:43:50,706 You'll just get the long tap. 2508 01:43:50,896 --> 01:43:51,956 >> So there's no way 2509 01:43:52,166 --> 01:43:55,246 that property gesture called [inaudible]? 2510 01:43:56,156 --> 01:43:59,146 >> You could potentially induce multiple ones. 2511 01:43:59,586 --> 01:44:02,846 You can give priority to them effectively by listening 2512 01:44:02,846 --> 01:44:05,386 to which one fires first, and you can think of this again 2513 01:44:05,386 --> 01:44:07,696 as layers, as to which layer is going 2514 01:44:07,696 --> 01:44:10,166 to receive the gesture first 2515 01:44:10,166 --> 01:44:11,846 if you've added to multiple objects. 2516 01:44:12,216 --> 01:44:15,576 But for the case you describe, they'd be mutually exclusive. 2517 01:44:16,076 --> 01:44:18,516 Other questions? 2518 01:44:19,076 --> 01:44:25,596 So out of curiosity, how many people are leaning toward web 2519 01:44:25,596 --> 01:44:28,046 applications for their third and final choice of projects? 2520 01:44:28,786 --> 01:44:30,686 Did I give a bad answer there? 2521 01:44:30,686 --> 01:44:31,876 Okay. All right, a few. 2522 01:44:31,876 --> 01:44:33,406 And iOS applications? 2523 01:44:34,536 --> 01:44:36,366 And undecided? 2524 01:44:37,406 --> 01:44:39,406 Okay. So not -- not bad. 2525 01:44:39,766 --> 01:44:42,336 So start thinking about that, even though I know you're 2526 01:44:42,336 --> 01:44:44,996 in the midst of Evil Hangman, but you'll soon get feedback 2527 01:44:44,996 --> 01:44:46,646 by this Wednesday from the teaching fellows 2528 01:44:46,646 --> 01:44:49,106 on the mobile local projects, so you can start thinking 2529 01:44:49,106 --> 01:44:50,916 about what you could've done better there, 2530 01:44:50,916 --> 01:44:52,786 how you might do things differently for a third 2531 01:44:52,786 --> 01:44:55,346 and final project if you go with HTML 5 and JavaScript. 2532 01:44:55,346 --> 01:44:57,716 Also think about the native applications and again, 2533 01:44:57,816 --> 01:45:00,006 when the specification goes up, you'll see that step one is 2534 01:45:00,006 --> 01:45:03,476 to float the idea by your TF, and he will confirm 2535 01:45:03,476 --> 01:45:05,066 or deny the appropriateness, 2536 01:45:05,066 --> 01:45:06,726 the viability given the limited time, 2537 01:45:06,726 --> 01:45:08,426 and will help guide you toward something that's doable, 2538 01:45:08,656 --> 01:45:10,946 so that in a few weeks' time, we'll all have some cake 2539 01:45:10,946 --> 01:45:12,556 and some exhibitions the projects. 2540 01:45:12,636 --> 01:45:13,506 Why don't we call it a night here, 2541 01:45:13,506 --> 01:45:14,526 and I'll stick around for questions. 2542 01:45:15,076 --> 01:45:15,646 See you at lab. 2543 01:45:16,516 --> 01:45:23,410 [ Silence ]