1 00:00:05,650 --> 00:00:06,770 Know what's up everyone. 2 00:00:06,770 --> 00:00:12,840 Mark right here at the slopes dot com and we've done some really cool stuff in our apps so far we've 3 00:00:12,840 --> 00:00:14,940 gotten the user interface built. 4 00:00:14,940 --> 00:00:18,310 We've got Segway so you can go back and forth between screens even now. 5 00:00:18,330 --> 00:00:23,430 Got a model built and I re-actions tied it to our league Visi and we don't let you go onto the next 6 00:00:23,430 --> 00:00:26,040 screen unless you've selected an option which is really cool. 7 00:00:26,040 --> 00:00:29,040 And then of course is stored in the player model. 8 00:00:29,040 --> 00:00:30,330 It's a struct. 9 00:00:30,480 --> 00:00:36,960 And so the next thing and possibly last thing we need to do here is actually pass data between View 10 00:00:36,960 --> 00:00:37,590 controllers. 11 00:00:37,590 --> 00:00:42,390 Now this is a topic that a lot of people struggle with and then they've done some really weird things 12 00:00:42,600 --> 00:00:47,280 to get data talking between View controllers going to make it really easy for you. 13 00:00:47,310 --> 00:00:47,740 OK. 14 00:00:47,760 --> 00:00:52,800 And the function that we're looking for here is already built in your view controller whenever you create 15 00:00:52,800 --> 00:00:56,180 a new one and it's called prepare for Segway. 16 00:00:56,360 --> 00:00:57,070 OK. 17 00:00:57,150 --> 00:00:59,070 And when you read a function by the way. 18 00:00:59,240 --> 00:00:59,750 OK. 19 00:00:59,770 --> 00:01:01,900 When you the actual function name. 20 00:01:01,950 --> 00:01:02,310 All right. 21 00:01:02,370 --> 00:01:03,390 It's going to look like this. 22 00:01:03,390 --> 00:01:05,760 Prepare for Segway. 23 00:01:05,760 --> 00:01:11,670 So this right here is the name of a parameter and this is the variable name that the parameter is going 24 00:01:11,670 --> 00:01:12,470 to take on. 25 00:01:12,750 --> 00:01:19,220 And so this this and this all kind of compose of the function definition of the function name. 26 00:01:19,290 --> 00:01:24,160 And if you have other subsequent parameters those will also be added to the name of the function and 27 00:01:24,180 --> 00:01:25,590 to show you what I mean. 28 00:01:25,920 --> 00:01:31,250 So this is right here all nice ready for us but if I type in the word prepare OK. 29 00:01:31,350 --> 00:01:35,570 Notice how it says prepare for Segway interface builder sender it's all right there. 30 00:01:36,760 --> 00:01:37,270 OK. 31 00:01:37,340 --> 00:01:38,680 So that's the function definition. 32 00:01:38,690 --> 00:01:39,690 OK. 33 00:01:39,710 --> 00:01:46,130 And it's an override function meaning the default view controller that you're inheriting from We'll 34 00:01:46,190 --> 00:01:50,960 call this and we don't need to call super on this or anything like that because we're overwriting it. 35 00:01:51,230 --> 00:01:54,260 Typically what that means is when you're writing and you don't call super. 36 00:01:54,260 --> 00:01:59,050 It means that you don't need the view controller implementation of it you don't need that code to run. 37 00:01:59,090 --> 00:02:01,550 Our code is going to take over from here. 38 00:02:01,550 --> 00:02:03,900 Otherwise super would call that parent code. 39 00:02:04,070 --> 00:02:10,390 OK so what we want to do is we want to see which side we were going to again remember what I said. 40 00:02:10,430 --> 00:02:15,350 I said if you have multiple segues that can be triggered from a single view controller you need to check 41 00:02:15,350 --> 00:02:16,240 which one is which. 42 00:02:16,250 --> 00:02:18,540 And you might pass different data to different segues. 43 00:02:18,560 --> 00:02:19,340 OK. 44 00:02:19,340 --> 00:02:22,820 In our case we only have one so it makes it really nice but we're still going to have to write the same 45 00:02:22,820 --> 00:02:25,470 code we would write if there were multiple segues. 46 00:02:25,610 --> 00:02:27,470 And this is the code. 47 00:02:27,470 --> 00:02:34,640 So if let And let's just say skill VC equals segue. 48 00:02:34,650 --> 00:02:38,710 Destination has skewl. 49 00:02:38,800 --> 00:02:41,070 VC All right. 50 00:02:41,110 --> 00:02:42,560 Let me let me break it down. 51 00:02:42,650 --> 00:02:42,960 OK. 52 00:02:42,960 --> 00:02:49,540 So what we're saying here is we're doing and if let's sequence and when and if sequence is OK. 53 00:02:49,680 --> 00:02:52,790 Basically it will try and run an operation. 54 00:02:52,980 --> 00:02:58,380 OK it'll try and run the statement in this case it's going to try and assign the destination view controller 55 00:02:58,410 --> 00:03:01,000 into this variable or this constant. 56 00:03:01,000 --> 00:03:02,060 The lead is a constant. 57 00:03:02,150 --> 00:03:02,390 OK. 58 00:03:02,400 --> 00:03:06,290 So it's going to try and do this if it succeeds it will execute inside the code block. 59 00:03:06,660 --> 00:03:09,780 If it fails then this statement will fail. 60 00:03:10,140 --> 00:03:10,490 OK. 61 00:03:10,510 --> 00:03:19,340 So if segue that destination so were the failure could happen is right here is as gate as with the question 62 00:03:19,340 --> 00:03:21,990 mark is saying let's grab the Segway destination. 63 00:03:22,070 --> 00:03:28,570 Well if you look at here at this destination by command click it destination is a type you view controller 64 00:03:28,590 --> 00:03:31,360 so it's just a generic view controller. 65 00:03:31,360 --> 00:03:36,850 But our destination that we want to go to is the skill of you know skilled VC does inherit from you 66 00:03:36,870 --> 00:03:37,800 view controller. 67 00:03:38,140 --> 00:03:46,540 And so with object oriented programming we can downcast a skilled VC or rather a destination view controller 68 00:03:46,540 --> 00:03:49,050 as a skill AVC because it does inherent. 69 00:03:49,060 --> 00:03:53,320 But let's say you skill AVC did not inherit from your controller it was just her own class. 70 00:03:53,320 --> 00:03:56,410 Then this would fill but it won't in this case. 71 00:03:56,500 --> 00:04:00,940 So what we're saying here is let's grab the destination that we're going to go to so it checks the Segway 72 00:04:01,930 --> 00:04:03,570 for the destination view controller. 73 00:04:03,580 --> 00:04:05,500 So the skill Visi in this case. 74 00:04:05,680 --> 00:04:06,340 OK. 75 00:04:06,610 --> 00:04:08,990 And then it's going to try and grab it. 76 00:04:09,010 --> 00:04:14,200 So it's going to grab the view controller code that exists what's in our storyboards So this file right 77 00:04:14,200 --> 00:04:18,420 here and OK it's going to load it in memory it's going to try and it's going to grab it. 78 00:04:18,700 --> 00:04:24,010 And of course it'll work because that's what's designed to work and it'll grab this code right here 79 00:04:24,100 --> 00:04:28,210 and it's going to send it back to you and store it here in this variable. 80 00:04:28,560 --> 00:04:29,310 OK. 81 00:04:29,380 --> 00:04:35,260 And the prepare for Segway happens whenever a Segway is triggered this prepare function is going to 82 00:04:35,260 --> 00:04:39,860 be called so it lets you do things before the Segway actually loads on the screen. 83 00:04:40,120 --> 00:04:42,940 And this is where you will pass data between View controllers. 84 00:04:42,940 --> 00:04:47,760 So again what we're doing here is we're saying it's the skill we see. 85 00:04:47,770 --> 00:04:52,180 So if we can grab it successfully then we're going to do something again and we had multiple controllers 86 00:04:52,180 --> 00:04:56,540 that you could choose from let's say there are five different screens you might go to based on the selection. 87 00:04:56,770 --> 00:05:00,080 Then what we would do is we would have like if let you know. 88 00:05:00,100 --> 00:05:05,610 And then you know else if let And then we would say you know other VC. 89 00:05:05,610 --> 00:05:09,400 And then we would cast a different Visi and then it would go down until it finds the proper one. 90 00:05:09,400 --> 00:05:10,560 And then we send the data. 91 00:05:10,680 --> 00:05:11,410 OK. 92 00:05:11,740 --> 00:05:15,040 So we're grabbing the next few controller we want to go to. 93 00:05:15,130 --> 00:05:17,000 And if this is confusing to you it's OK. 94 00:05:17,050 --> 00:05:18,880 You're just learning this takes time. 95 00:05:18,880 --> 00:05:22,720 You're going to do this many times over and you can always watch this video again. 96 00:05:22,750 --> 00:05:22,930 OK. 97 00:05:22,930 --> 00:05:26,020 So grab the skill Visi and what we want to do. 98 00:05:26,020 --> 00:05:27,800 We want to pass data into it. 99 00:05:27,850 --> 00:05:35,010 So we're going to need to do is store a player variable in our skewl VC and we don't have one yet so 100 00:05:35,020 --> 00:05:36,050 let's do that now. 101 00:05:36,340 --> 00:05:45,200 So over here let's go ahead and say var player type player and let's do it in Italy unwrapped optional. 102 00:05:45,220 --> 00:05:51,100 What that means is no matter what we promise we promise that there's going to be code in there that 103 00:05:51,100 --> 00:05:52,270 it's not going to be nil. 104 00:05:52,380 --> 00:05:53,290 OK. 105 00:05:53,350 --> 00:05:55,080 And so that's what we're promising. 106 00:05:55,090 --> 00:06:02,410 And so what we're going to do is we're going to go over here and we're going to say skill Visi top player 107 00:06:02,530 --> 00:06:07,830 the one that we just created OK and did not save the file. 108 00:06:14,180 --> 00:06:18,690 Skill we up player there we go. 109 00:06:18,690 --> 00:06:19,400 Now it's popping up. 110 00:06:19,440 --> 00:06:19,910 OK. 111 00:06:20,070 --> 00:06:23,750 So skill obviously the player equals player. 112 00:06:24,090 --> 00:06:25,510 You're like what's going on here. 113 00:06:25,530 --> 00:06:27,310 These names of the same. 114 00:06:27,330 --> 00:06:31,260 Well we are referring to the player that we saved and this view controller here. 115 00:06:31,430 --> 00:06:31,760 OK. 116 00:06:31,780 --> 00:06:33,660 This is here in league visi. 117 00:06:33,690 --> 00:06:35,630 We've set the player here. 118 00:06:36,210 --> 00:06:41,460 And what we're doing is we are just passing this player from the screen onto the player on the screen. 119 00:06:41,460 --> 00:06:45,690 So literally this is where the handoff comes you know like footballs being handed off UK. 120 00:06:45,810 --> 00:06:51,210 Same exact thing we're handing off the data from the player on the league Visi and we're storing it 121 00:06:51,300 --> 00:06:53,750 in the player in the school of visi. 122 00:06:53,940 --> 00:07:01,740 Now something really important to understand when you are in prepare for segue this will always always 123 00:07:02,220 --> 00:07:09,600 always always be called before you did lotas called on the destination view controller. 124 00:07:09,600 --> 00:07:19,230 So remember this very important prepare for Segway is always called before you did load on the destination 125 00:07:19,230 --> 00:07:19,810 view controller. 126 00:07:19,830 --> 00:07:26,700 So what you can do is you can always guarantee that data will be available in view to load if you initialized 127 00:07:26,700 --> 00:07:26,790 it. 128 00:07:26,790 --> 00:07:35,680 So if I was to do something like this player datt desired League. 129 00:07:36,640 --> 00:07:40,650 OK if I was to do that it will not be nil. 130 00:07:40,750 --> 00:07:42,200 It can't be OK. 131 00:07:42,550 --> 00:07:46,330 And it says expression implicitly coerced from string. 132 00:07:46,330 --> 00:07:53,800 Now here in our player model it's because we have them as optionals And you know probably here we should 133 00:07:53,800 --> 00:07:58,330 have these as implicitly unwrap the optionals as well too because we have to have data in order for 134 00:07:58,910 --> 00:07:59,980 this to happen. 135 00:08:00,070 --> 00:08:03,020 For this app to run and this can be very confusing OK. 136 00:08:03,290 --> 00:08:07,830 Do I make it optional do I make it implicitly unwrapped optional so remember this. 137 00:08:07,870 --> 00:08:09,990 OK here is the rule. 138 00:08:10,510 --> 00:08:17,650 If you can promise that data is going to be there mean your app must have data in order to run. 139 00:08:17,740 --> 00:08:20,950 Then you can make it an implicitly unwrapped optional. 140 00:08:20,950 --> 00:08:24,970 If you don't know whether data is going to be there or not and that's part of your design. 141 00:08:25,180 --> 00:08:27,580 OK it must be an optional. 142 00:08:27,700 --> 00:08:32,650 OK so if you are promised data is going to be there because your app can't run without it you can assume 143 00:08:32,650 --> 00:08:35,230 it's going to be there and make it implicitly unwrapped. 144 00:08:35,290 --> 00:08:39,010 If there was no data in here and you tried to access it yes it would crash but you're promising that 145 00:08:39,010 --> 00:08:43,630 there's going to be data there whereas the optional saying well might application design means that 146 00:08:43,630 --> 00:08:44,350 there might not be data. 147 00:08:44,350 --> 00:08:46,180 Maybe it's optional field who knows. 148 00:08:46,180 --> 00:08:47,840 So that's the rule. 149 00:08:47,890 --> 00:08:49,360 And again it could be confusing. 150 00:08:49,360 --> 00:08:51,350 It takes lots of practice but you'll get it. 151 00:08:51,680 --> 00:08:57,710 So this morning should go away and there you go. 152 00:08:57,720 --> 00:09:01,350 And so what we're doing is we're going to print this here so let's just go ahead and run our app and 153 00:09:01,350 --> 00:09:03,400 see if it actually prints as expected. 154 00:09:04,210 --> 00:09:08,520 So what should happen is we're going to select the desired League. 155 00:09:08,560 --> 00:09:08,990 OK. 156 00:09:09,040 --> 00:09:12,520 We're going to go to the next screen and when the next screen loads we print it should show the desired 157 00:09:12,520 --> 00:09:13,980 league that we selected. 158 00:09:14,020 --> 00:09:16,110 Hypothetically if we wrote the code correctly 159 00:09:24,310 --> 00:09:24,660 OK. 160 00:09:24,710 --> 00:09:26,790 So get started. 161 00:09:26,840 --> 00:09:28,590 Let's go ahead and select the women's league. 162 00:09:28,880 --> 00:09:32,330 And when I click Next I should see women's printed here on the screen. 163 00:09:33,830 --> 00:09:35,590 And sure enough it was OK. 164 00:09:35,630 --> 00:09:37,340 So are you with me so far. 165 00:09:37,670 --> 00:09:40,720 What happened was we triggered her segue. 166 00:09:40,790 --> 00:09:43,040 So right here. 167 00:09:43,060 --> 00:09:44,340 See this performed segue. 168 00:09:44,380 --> 00:09:46,360 We triggered that from the next button right. 169 00:09:46,420 --> 00:09:48,710 And we said let's load the skill AVC So this is called. 170 00:09:49,000 --> 00:09:52,500 And then the very next thing that's called is prepare for segue. 171 00:09:52,540 --> 00:09:57,790 And this is where we pass data from this view controller into the next using this code here and we set 172 00:09:57,790 --> 00:09:58,750 the data that we need. 173 00:09:59,810 --> 00:10:03,560 And it doesn't have to be in this very well we could call the function that sets it in a variable but 174 00:10:03,560 --> 00:10:10,070 somehow some way we need to set data on the destination view controller then the destination view controller 175 00:10:10,070 --> 00:10:14,560 which was the skill Visi in view to load our data is already ready to go. 176 00:10:14,600 --> 00:10:16,580 And you could print it and use it accordingly. 177 00:10:16,580 --> 00:10:19,620 So we've kind of just built the app right. 178 00:10:19,690 --> 00:10:22,460 What we've done is we built an app that has three screens. 179 00:10:22,460 --> 00:10:24,610 We've learned how to set data from some fields. 180 00:10:24,610 --> 00:10:30,390 We selected a field we stored in a model and then we passed that data model between View Controller 181 00:10:30,410 --> 00:10:34,910 so we can use it and you could continue to do this we could call another performed from Segway and another 182 00:10:34,910 --> 00:10:38,860 prepare and pass it on to the next one and pass it on to the next one and then the next one. 183 00:10:38,870 --> 00:10:42,730 Now if you're thinking that's a lot of work do we really want to pass data from view control of your 184 00:10:42,740 --> 00:10:43,850 controller. 185 00:10:43,850 --> 00:10:48,350 And I would say no later on you're going to learn how to work with some different design patterns like 186 00:10:48,350 --> 00:10:51,780 the singleton pattern where you have a central source that holds all your data. 187 00:10:52,040 --> 00:10:54,130 And that's a lot nicer than passing things through. 188 00:10:54,140 --> 00:10:56,290 But this is a very common practice as well too. 189 00:10:56,360 --> 00:11:02,360 And this is in the Apple documentation we've done everything exactly as Apple teaches in their documentation 190 00:11:02,390 --> 00:11:05,470 and it's very useful So that's it for now. 191 00:11:05,480 --> 00:11:07,130 This is really good stuff. 192 00:11:07,130 --> 00:11:11,960 Core foundational things that you need to know everything that I've taught you on the swish app. 193 00:11:11,960 --> 00:11:16,160 You have to know it now and if you ever want to get a job in industry you have to know everything we've 194 00:11:16,160 --> 00:11:17,440 done in this app by heart. 195 00:11:17,540 --> 00:11:18,130 OK. 196 00:11:18,380 --> 00:11:21,530 There's nothing overly complex but the things that we have learned here you have to know by heart in 197 00:11:21,530 --> 00:11:25,820 order to get a job if you know if you don't know these things that are in this lesson you're not ready 198 00:11:25,820 --> 00:11:30,270 for a job yet so you're going to need to master these very basic principles because this is what you're 199 00:11:30,270 --> 00:11:32,660 going to doing most of the time in your app development. 200 00:11:32,660 --> 00:11:34,010 So that's it for now. 201 00:11:34,010 --> 00:11:36,520 Marc price at Dev slopes dot com. 202 00:11:36,560 --> 00:11:37,880 Movin on and forward.