0 1 00:00:00,450 --> 00:00:00,750 All right. 1 2 00:00:00,780 --> 00:00:05,640 So in order to use UserDefault, we have to create a brand-new object. 2 3 00:00:05,640 --> 00:00:13,080 So let's call it defaults and we'll set it to equal UserDefaults which is an interface to the user's 3 4 00:00:13,080 --> 00:00:19,640 default's database where you store key-value pairs persistently across launches of your app. 4 5 00:00:19,650 --> 00:00:21,270 That's exactly what we want. 5 6 00:00:21,330 --> 00:00:26,190 So let's hit UserDefaults and we're gonna set up a standard UserDefault. 6 7 00:00:26,190 --> 00:00:32,940 So, now that we've got that setup, we can go down to the part where we add a new item to our to-do list 7 8 00:00:33,540 --> 00:00:39,860 and we append it to our itemArray which is this thing here. 8 9 00:00:39,930 --> 00:00:48,930 Now, what we can do is we can save that updated item array to our UserDefaults and we can do that in 9 10 00:00:48,930 --> 00:00:51,250 a single line of code by writing 10 11 00:00:51,360 --> 00:00:58,050 defaults.set and we're going to use value for key which takes any object, 11 12 00:00:58,050 --> 00:01:02,000 and in this case, it's going to be an array or rather self.itemArray 12 13 00:01:02,000 --> 00:01:04,330 because, remember, we're inside a closure here. 13 14 00:01:04,500 --> 00:01:10,100 And the key is going to identify this array inside our UserDefaults. 14 15 00:01:10,110 --> 00:01:13,730 So let's call it "TodoListArray." 15 16 00:01:14,070 --> 00:01:20,850 And, of course, because we're inside a closure, we have to add "self" to our defaults as well, and see if 16 17 00:01:20,850 --> 00:01:21,780 it works. 17 18 00:01:21,780 --> 00:01:23,550 All right, let's go ahead and add a new item. 18 19 00:01:26,320 --> 00:01:29,340 Hit Add Item, shows up in our table view, 19 20 00:01:29,620 --> 00:01:37,700 But as you'll see, if I delete our app and reopen it again, it does not show up. 20 21 00:01:37,840 --> 00:01:44,140 And the reason is not because our code didn't work or that we didn't manage to save our item array into 21 22 00:01:44,140 --> 00:01:45,100 our defaults, 22 23 00:01:45,100 --> 00:01:50,790 the reason is because we haven't used our saved item to load up the TableView. 23 24 00:01:50,800 --> 00:01:56,340 It's still getting all of that data from our itemArray which does not persist. 24 25 00:01:56,350 --> 00:02:05,260 Remember? But we can actually view our data inside our UserDefaults and we can prove that the data has 25 26 00:02:05,260 --> 00:02:06,540 been saved. 26 27 00:02:06,550 --> 00:02:14,260 Now, UserDefaults get saved in a plist file, and that's why everything you put in there has to be a 27 28 00:02:14,260 --> 00:02:15,770 key-value pair. 28 29 00:02:16,080 --> 00:02:24,180 So you always need a key that you're going to use to retrieve the item, and then you add the value. 29 30 00:02:24,310 --> 00:02:25,270 It could be anything. 30 31 00:02:25,270 --> 00:02:27,990 It could be an array. It could be a dictionary, string, 31 32 00:02:28,210 --> 00:02:33,250 any data type in there. And you can grab it back using this key. 32 33 00:02:33,250 --> 00:02:41,850 So how can we find our UserDefaults file so that we can see our data? In order to do that, 33 34 00:02:41,890 --> 00:02:52,300 we need to grab the file path of our sandbox that our app runs, we need to get the ID of the simulator, 34 35 00:02:52,700 --> 00:02:58,040 and we also need the ID of the sandbox where our app lives in. 35 36 00:02:58,270 --> 00:03:02,150 Now, it sounds a little bit complicated, but it's actually quite simple. 36 37 00:03:02,200 --> 00:03:04,860 Let's go into our AppDelegate at the 37 38 00:03:04,930 --> 00:03:07,640 "didFinishLaunchingWithOptions" 38 39 00:03:08,020 --> 00:03:11,290 delegate method which we know always gets called. 39 40 00:03:11,440 --> 00:03:17,170 And here, we're going to write a little bit of code in order to printout the path for our UserDefaults 40 41 00:03:17,170 --> 00:03:17,880 file. 41 42 00:03:17,890 --> 00:03:24,550 Now, at this point, if you want to follow along with me and see this file path, make sure that you run 42 43 00:03:24,550 --> 00:03:31,690 your app inside the simulator, and not a physical device, and also that you've added a new item to your 43 44 00:03:31,690 --> 00:03:32,930 table view. 44 45 00:03:33,010 --> 00:03:36,150 So let's go ahead and print this search path. 45 46 00:03:36,190 --> 00:03:46,830 So it's NSSearchPathForDirectoriesInDomains and the directory is the documentDirectory and 46 47 00:03:46,830 --> 00:03:53,530 the domain mask is the userDomainMask and expand tilde will go for true, 47 48 00:03:53,550 --> 00:04:00,070 and then we're going to get the last item in this array, and we're going to print it as a string. 48 49 00:04:00,090 --> 00:04:02,580 Now, don't worry too much about this line. 49 50 00:04:02,610 --> 00:04:09,480 I'm just using it to print and to prove to you that our data has been saved somewhere, even though it's 50 51 00:04:09,480 --> 00:04:10,530 not showing up. 51 52 00:04:10,530 --> 00:04:17,490 So let's run our app again. And as soon as our app launches, we can see this file path here. 52 53 00:04:17,490 --> 00:04:24,360 Now, we can use that file path to go into our Finder and try and locate this plist file that stores 53 54 00:04:24,360 --> 00:04:25,170 our data. 54 55 00:04:25,170 --> 00:04:30,200 So this starts off in our root which is our Macintosh hard drive, 55 56 00:04:30,390 --> 00:04:32,910 and then we're supposed to go into users, 56 57 00:04:33,090 --> 00:04:36,150 and this is my user name on this laptop, 57 58 00:04:36,210 --> 00:04:39,860 and then we're going to go into Library, Developer, 58 59 00:04:42,930 --> 00:04:52,710 CoreSimulator, Devices,and we have to search for this 8D49. 59 60 00:04:52,720 --> 00:04:53,560 It looks like that one. 60 61 00:04:53,680 --> 00:04:56,920 So this is the device ID. 61 62 00:04:56,920 --> 00:05:04,210 So this is called a UUID, and it identifies our device uniquely, so that could be our simulated device 62 63 00:05:04,300 --> 00:05:06,610 or it could be a physical device. 63 64 00:05:06,610 --> 00:05:13,630 So this corresponds to this particular simulated instance that I've got launched here. And then I have 64 65 00:05:13,630 --> 00:05:23,610 to go in into Data, Containers, Data again, Application, and then I have to search for the Application. 65 66 00:05:23,800 --> 00:05:31,030 And that refers to the unique ID of this Todoey application that I've launched earlier on where I 66 67 00:05:31,030 --> 00:05:32,470 saved my data. 67 68 00:05:32,470 --> 00:05:39,160 So, now we're entering the sandbox, essentially, and this is going to be called E5. 68 69 00:05:39,220 --> 00:05:46,450 So let's look for something that is E5. Now a much easier way to do this would actually be sorting 69 70 00:05:46,450 --> 00:05:47,540 this or searching it, 70 71 00:05:47,620 --> 00:05:49,020 but I found it right there. 71 72 00:05:49,030 --> 00:05:50,710 So E50. 72 73 00:05:50,710 --> 00:05:54,830 This is basically our app, Todoey. Now, it would be easier if they called it Todoey, 73 74 00:05:54,880 --> 00:05:56,640 but then that wouldn't be unique. 74 75 00:05:57,100 --> 00:05:59,160 So here's our app sandbox. 75 76 00:05:59,170 --> 00:06:05,530 And once you've gotten here, you're going to look inside Library and Preferences. 76 77 00:06:05,530 --> 00:06:09,470 And now, finally, you get to your plist, 77 78 00:06:09,520 --> 00:06:14,060 and if we expand it, you can see that it says, 78 79 00:06:14,080 --> 00:06:16,390 "com.londonbrewery.Todoey/plist. 79 80 00:06:16,390 --> 00:06:23,680 Now, if we double click on it, it'll open by default inside Xcode, and you'll see that we have this key 80 81 00:06:23,860 --> 00:06:31,240 that we used earlier on where we said save it under the key "TodoListArray," TodoListArray here, 81 82 00:06:31,270 --> 00:06:39,700 that's the key, and the value is an array. So Swift is clever enough to figure out that our item, the data 82 83 00:06:39,700 --> 00:06:42,520 type was an array data type. 83 84 00:06:42,640 --> 00:06:47,530 And if we expand this, we can see that there's four items in there, 84 85 00:06:47,590 --> 00:06:51,740 and our latest item was in fact saved. 85 86 00:06:51,790 --> 00:06:54,490 So why is it not showing up in our table view? 86 87 00:06:55,120 --> 00:06:59,960 Well, it's because we haven't used it to retrieve the data. 87 88 00:07:00,070 --> 00:07:08,920 Now, all we need to do in order to retrieve our data is we can go into viewDidLoad and we can set our 88 89 00:07:08,950 --> 00:07:15,990 itemArray to equal the array inside our UserDefaults. 89 90 00:07:16,060 --> 00:07:23,120 So itemArray = defaults.array forKey, 90 91 00:07:23,120 --> 00:07:27,510 the key is, of course, "TodoListArray." 91 92 00:07:27,610 --> 00:07:30,840 Let's just double check because it's a hardcoded key. 92 93 00:07:30,910 --> 00:07:34,540 Just make sure that it's exactly spelt the same. 93 94 00:07:34,540 --> 00:07:35,980 Yeah, looks good. 94 95 00:07:36,130 --> 00:07:40,950 And we're going to cast this as an array of strings. 95 96 00:07:40,990 --> 00:07:48,400 So that's all very well and good if our TodoListArray actually exists. But if it doesn't, then our 96 97 00:07:48,460 --> 00:07:51,330 app is probably going to crash. 97 98 00:07:51,370 --> 00:07:53,030 So to prevent this, 98 99 00:07:53,230 --> 00:08:04,960 instead, we can write this as if let items = defaults.array forKey as array of strings, 99 100 00:08:04,960 --> 00:08:14,820 And if that works, then, let's say, itemArray is now equal to items. And we can get rid of that force 100 101 00:08:14,820 --> 00:08:15,510 downcast, 101 102 00:08:15,520 --> 00:08:16,750 make it an optional. 102 103 00:08:16,750 --> 00:08:20,350 So, now let's run our app and see if it works. 103 104 00:08:20,420 --> 00:08:20,820 Hey. 104 105 00:08:20,830 --> 00:08:26,750 So our last item that we saw inside the plist now exists inside our table view, 105 106 00:08:26,950 --> 00:08:35,350 and also if I add any new items, then it also shows up in our table view. And you can see it appear both 106 107 00:08:35,350 --> 00:08:40,330 in the UserDefault plist, as well as when we terminate our app and reopen it. 107 108 00:08:40,330 --> 00:08:47,320 So that was a quick intro into how we can use UserDefaults to persist data. 108 109 00:08:47,320 --> 00:08:52,900 Now, in the next lesson, we're going to talk about the UserDefault in a little bit more detail and talk about 109 110 00:08:52,900 --> 00:08:56,910 which scenarios and situations should you be using this. 110 111 00:08:56,920 --> 00:08:59,400 So all of that and more on the next lesson. 111 112 00:08:59,440 --> 00:08:59,920 See you there.