Do you have an idea for an app that you think would be useful to others, but you don't know how to make it a reality? You're not alone! Lots of people are interested in app development, but they aren't sure how to turn their idea to code and then into a finished app. From first steps to Xcode, we'll explain the building blocks you need to turn your iOS app idea into reality.
Hi everyone! Good morning! Thanks, everyone, for being here today. My name's Jesse Pease. And I'm an engineer on the Health Engineering Team. And today, I'm going to show you how to make your very first app.
So today we're going to step out of our comfort zones. We're going to explore, and we're going to start building our dream app.
You know that one that you've had in the back of your mind while you're waiting in line for your coffee in the morning? Or that one that you drew out on your napkin on the flight out here to WWDC? Or that one that you tell your friends about and make them promise not to tell anyone else? That one. That's the idea we're going to start working on today. As Joseph Chilton Pearce said, "To live a creative life we must lose the fear of being wrong." And when we start building new ideas, we're bound to run into bumps in the road.
But our goal today is to show you all the building blocks you need to make your dream app a reality. We're going to start off today by organizing our ideas.
Then we're going to learn how to navigate Xcode. And then build a simple game using Swift.
Now familiarity with a programming language will help you today.
But if you're new to Swift or looking for a helpful resource, I recommend downloading the App Development with Swift book from the Apple bookstore.
Or checking out the Swift Playgrounds app for iPad. Later is going to show you how to add multiple views within your app and then persist in display data for your users over time.
So Tono and I were recently at a unicorn petting zoo.
Yes, we actually have these in California. And we were after having this experience countless times of waiting in line.
We decided that we needed to make something to keep ourselves occupied while we wait.
So we decided to make a game.
Something quick and fun to keep us occupied for a short amount of time.
And I said, "Well, of course if we make a game, it has to have unicorns." But then we needed something that people would want to avoid.
And so we decided to make a whack-a-mole-type game with unicorn and poop.
And then incorporate scores and eventually a leaderboard to keep track of our scores over time. Because we have a little bit of a competitive nature. So let's take a look at what this game play looks like.
Upon pressing start game, a random emoji's going to appear somewhere randomly on the screen.
Either a unicorn or a poop. At that point, the user has one second to click that button.
Now, if they hit the unicorn, then they get one point.
Then if they accidentally tap the poop, then the game is over.
But in addition to this, if they miss the unicorn, the not-so-lonely unicorn, and so they automatically lose the game.
So the goal is hit all the unicorns. Don't hit the poops.
Let's take a look at this.
Get it! Nice! Get that unicorn.
Oh! There we go, one more. Oh! Oh, shoot. Moving too quickly and accidentally hit a poop.
Let's jump right in.
So for those of you who aren't familiar, Xcode is a tool we use on macOS to help build iOS, macOS, watchOS, and tvOS apps. You can download it from the App Store if you don't have it already.
So when we open up Xcode, we first want to select create a new Xcode project.
After this, we see all the different type of app templates that we can create.
In our case, we're going to select single view app.
But notice here that you could also select a page based app, a sticker pack app, or even a game.
But our game is very simple, so we will just stick with single view app. And then hit next. From here we type in our app name, which in our case is Disappearing Unicorns. And our ex-- , our team name is Example Team.
And hit next.
After we choose a place to save our app, we're dropped into the project settings. Now we won't be making any changes here today, so we'll go ahead and look at the other important files in our Project Navigator on the left-hand side.
The first one is the AppDelegate.
An AppDelegate is created for each app, and it helps us manage the lifecycle of our app over time.
There's certain methods that can be called when we're going into the background or coming into the foreground.
But we won't be making any changes with our AppDelegate today either.
Next I'm going to select the main storyboard file.
The storyboard is where we create the UI or the user interface for our app.
And where we can add all of the UI elements like buttons, labels, or images.
But it's not just where we create that one single view. It's also where we lay out all of the logical flow for our app over time. The story.
Next we'll select the view controller.
The view controller helps us control out view, and this is where we'll write the logical code for our app. Well let's talk about how we create our views within our storyboard.
Let's navigate back over to the main dot-storyboard file. And at this point, make sure not to select the launchscreen.storyboard.
The launchscreen storyboard is what we use to create the view for when our app is being launched or loaded onto the screen the first time.
You'll notice in the upper right-hand corner of our storyboard here that there's an object library button. This is a button with a circle and a little square inside.
This is where we can take things like buttons or labels or images and drag them onto our storyboard.
On the left-hand side, you'll see the outline view for our app.
And if you click the little disclosure triangle, you'll see all the different things that are currently on our storyboard. Now you're thinking to yourself, "There's nothing on this storyboard. Why is this helpful?" Well, in the future, you may have lots of elements on your storyboard.
And eventually you may not be able to find something because it could be under something else. Or maybe you've accidentally created duplicates. So this is a great place to go if you're looking for all of the elements that you've put on your storyboard.
Alright. Let's go ahead and jump into our demo and start making our app. So here I'm going to go over to my computer where I already have Xcode launched.
Okay. And I have my Disappearing Unicorns file. Here I'm navigating to the main storyboard. And let's go ahead and start off by adding all of those UI elements that we need to create our game.
So I'm going to go up to the object library. And I can scroll through here and see all of the different things that I can put on there.
We have labels, buttons, text fields, activity indicators, even images.
But let's start off with that start-game button. So here I'll search for button.
And click and drag the button to the center of my storyboard.
Here I'll double click to change the text to start game, exclamation point. But this is a little bit small.
So in order to make this larger, I can go to the upper right-hand corner of Xcode and open up the Inspector pane. And then select this little slider button which is the Attributes Inspector.
This is where we change attributes of the items on our storyboard.
In this case, I'm going to make my font much bigger.
From size 15 to size 50.
And hit done. Now to quickly create copies of items on our storyboard, I can hold down the option key and click and drag on my storyboard to quickly create another copy of this button.
And so in this case, I'm going to change start game to the emoji for a unicorn. And to pull up the emoji keyboard, I can hit the control-command-space key and select unicorn.
Great! Let's go ahead and make a quick copy of this as well for our poop.
Control-command-space and poop.
Awesome. And one more button for our leaderboard button.
So click, option, drag.
Double click leaderboard. Uh-oh. Not all caps.
And change our font here from size 50 to size something much smaller. Maybe 25. Awesome.
Now we need one more element on our storyboard which is a label for our points.
So go back to my object library and search for label. And then click and drag this onto the screen.
Here I'm going to change this text to be zero.
And then change the font to something much larger like size 90.
Awesome! There we go. Now we have all of the UI elements that we need to create our game.
Let's go ahead and start connecting our UI to our code.
Now to have both the storyboard and the view controller code up at the same time, I can open up this Assistant Editor. It's the button with two overlapping circles.
Awesome. Now there's a bunch of different types of connections that we can make between the objects on our storyboard and our code.
Now the first type is called an outlet, and an outlet lets us refer to our user interface within our code.
Let's start out by creating an outlet for this start game button.
To create an outlet, I select the start-game button on the storyboard, hold down the control key, and click and drag over to my storyboard. Sorry, over to my view controller code, and let go.
At this point, I change my connection from-- type-- oh, it's already outlet. Perfect. And I'm going to name this start game button and hit connect.
Awesome. Now we have a connection between our code and our storyboard. And we can double check that this connection was made correctly, by seeing this little gray circle to left of start-game button. If we hover over it, it highlights the item on our storyboard that is connected to this code. Now, in the interest of time, I've already written the code for our other outlets.
But you'll notice that to the left of them, they have open circles. This means that they haven't been connected to our storyboard yet.
To make the connections, we just click inside the circle to the left of good button in this case. And drag over to our unicorn button which is the button we want to be associated with this line of code. And let go.
We'll do the same thing for bad button, leaderboard button, and points label.
Awesome. Now all of these connections have been made.
Now another type of connection we can make is called an action.
And an action is a piece of code that's linked to an event that can occur within our app.
In this case, I want an action method for whenever my start-game button is pressed.
So to create this connection, I could hold down the control key once again with the start-game button and click and drag over to my view controller code. And let go. This time I will change my connection to type action and name this start pressed. And I want my event to be a touchup inside event, and hit connect.
Awesome. You'll notice that there's this closed circle once again. And when I hover over it, the start-game button is highlighted.
Now I've already written two other action methods for both our good pressed and our bad button pressed.
But I actually want to make a different type of connection this time.
I want to create an event or an action event for when I press down on my button.
Because I want my user to get the point immediately when they touch the button. Not when they've touched down and then back up. I want to select the object that I want to be associated with this action. In this case, my good button or my unicorn.
Then go back to my Inspector pane and click on this little button with the circle with a little arrow inside. This is called our Connections Inspector. From here you'll see all the different types of sent events that I can create a connection for. In this case, I want to create a connection for the touch-down event.
I'll click inside this open circle, and drag over to the action method that I want to be associated with this event. And let go. I'll do the same thing with my bad button.
Touch-down, click, and drag over to bad pressed and let go. Okay, great.
Just two more things that we want to do before we can build and run our app for the very first time.
The next thing we want to do is we want to do a little bit of set-up for our app.
And we can do this in a method called viewDidLoad.
And a viewDidLoad is created for a view controller at the very beginning automatically.
And in here, what I want to do is a bit of setup. In this case, I want to hide some things. The first thing I want to hide is that points label. I don't want that on the screen the very beginning of our game.
So I'll just type points label dot-- hmm.
How about hide? Oh look? Looks like there's a property called isHidden. And if I hit enter, it'll autocomplete into Xcode for me.
To see what isHidden does, I can hold down the option key on my keyboard, hover over isHidden and click. When I do this, I can read a bit more about what isHidden is, and what I can do with it. In this case, I see that it's both a getter and a setter. Which means that I can set isHidden equal to true, and it should hide my points label at the very beginning of my game. Now I also need some variables to keep track of my gameplay over time. And I've already written these, so I'll quickly add them using a shortcut.
One of them needs to be, it's already initialized, but I actually need to populate it with some data. And that's this game buttons list.
Now you're thinking to yourself, "Jessie, if we only have a unicorn and a poop, why would we need to create a whole array of buttons?" Well, in our case we want to make our code more extensible which means make it easier to build on over time. Because in the future, we may have more than just the unicorn and the poop. We may have a thumbs-up emoji. We may have a frowny-face emoji.
So in this case, we want to say that game buttons equals list of good button and bad button.
Okay. I've also written some helper methods that will help us with our gameplay.
I'm going to add those now.
One of them is this method called set up fresh game state.
You'll notice that it makes sure that the start game and leaderboard button are unhidden. They're onscreen.
It hides my gameplay buttons, and it sets up some initial values for my points.
So here in my viewDidLoad, I also want to call up set up fresh game state.
You'll notice here as I'm typing, Xcode is autocompleting all of the things that I could possibly put as some code. In this case, if I hit enter with set up fresh game state already highlighted, it'll automatically populate it for me. Okay. One last thing we want to do, and then we can build and run our app.
Just for sanity, in my start pressed method, action method, I'm going to put a print statement here.
And say start game button was pressed.
And I expect that every time I press that start-game button, this line of code will be logged to my console.
I can show my debug area by opening up this middle button here with the line on the bottom of the square.
I'm going to hide my Inspector pane. I don't need that anymore.
Okay. It's finally time. We can build and run our app.
Now in the upper left-hand corner, you'll notice that my app name, Disappearing Unicorns, with a little arrow to an iPhone 10.
If I click on iPhone 10, I can see all the different simulators that I can run my app on.
Now a simulator is a simulation of a device on my Mac.
And in this case, I want to select iPhone 10.
Now if I had plugged my phone into my computer, I could also build and run my app on my own device which is pretty cool.
So with iPhone 10 selected, I can click this play button here. This will build and run my app in my simulator.
Here we go.
Oh, nice! Okay, so when I press this start-game button, I should see that the start-game button was pressed is logged in my console down here.
Awesome! We've just created a UI, and we've connected it to our code.
Let's jump back over and start talking about the game logic for our app.
Okay, so in the very beginning of our game, we know we have that start screen, and it has two buttons on it. It has that start-game button and that leaderboard button. But we're just talking about the gameplay right now. So we're going to wait for the start-game button pressed. And once that button is pressed, we drop into playing mode.
And at the beginning of playing mode, we get a random emoji in a random location on the screen. Either a unicorn or a poop.
At that point, we set a timer for one second to allow our user to have time to interact with our button.
Now at the end of that one second, if the user did not press a unicorn, then the unicorn was lonely, and they lose.
And if they successfully avoided tapping a poop, then they get another round of the game.
Now we also want to say what happens if they actually do press one of the buttons during the game.
Well if they press the unicorn button, we give them another round of the game and give them a point.
Otherwise, if they accidentally select the poop, then game over.
Okay. Let's talk about what this code looks like.
We'll start off with the start screen. Now we're going to break up our code into logical blocks. And in our case, we're going to use methods to do this. So that it's not just one long file full of lots of code. And it's easier for us to look at very specific parts.
The first method we're going to write is called start new game which we're going to call from start pressed.
This is going to do some setup for the beginning of a game route.
The first thing that happens in start new game is that we need to hide that start-game button and hide that leaderboard button.
Then we need to update our points label and set it to zero.
And we can even do some cool things here like dynamically change the color of our points label throughout our code. And here I'm going to set that text color to magenta during active gameplay.
Finally at the end of setting up my start new game, I'm going to call the first round of my game.
Okay? Let's look at that. In our one-game round, we first update our points label, make sure that it's up to date.
Then we display a random button. Either that unicorn or that poop in a random location on our screen.
I've written this helper method display random button that chooses a random x and y coordinate to place our button.
Then we set a timer for one second.
Now, if this timer goes off after one second, then the code inside the block of the timer will get called.
And in that case, we want to check if the current button that's on screen is a unicorn, then the game is over. Because the user left a lonely unicorn again. Otherwise, if they successfully avoided the poop and that's still onscreen, they get another round of our game.
Now let's talk about what happens if they did press one of our buttons.
Well if they pressed the good button, we want to give them another point.
We actually want to cancel our timer. And we're going to do this by invalidating it so that it doesn't go off, and then we'll call another round of our game. And if they press the bad button, well let's hide that button and get it out of the way so that they can't interact with it again.
We'll cancel the timer again by calling invalidate on it. And then call game over which is a helpful method that I've written to help end the game.
Okay, let's add this game logic into our game.
Going to go back over to our Xcode project. And in this case, I don't need my storyboard up anymore. I'm just going to be making changes to my view controller.
So I can select here the standard editor, and then select my view controller from my Project Navigator.
Now, we've already written our code in our slides.
So I'm going to just quickly add it into our view controller using some shortcuts. So here we have start new game where we hide our start game and our leaderboard button. Set up some initial stuff with our game points, and then call one round of our game.
Then we need our one-game round.
And here we update our points label, display random button, and call our timer.
And finally we need to put the code and for the logic in our both our start pressed. And our good pressed.
And finally our bad pressed. Okay. We have all the code we need. Let's see how it goes. Here I'm going to click this play button again to build and run our app in the simulator.
Okay, I'm nervous. Let's go.
Oh! Got one! Where's another? There's a lot of poops.
There we go. Okay, I could seriously play this all day, but I probably should let show you how to incorporate a leaderboard. Whew! So I'm going to try and lose on purpose here.
Oh, there we go.
Okay. Wow, yeah. That's great.
That was incredible! We just made a game in less than 30 minutes.
Just think about what you could do if you had more time.
So we first started out by learning to navigate Xcode.
Then we created a simple UI using our storyboard and connected that UI to our code. And finally we wrote game logic using Swift.
All in less than 30 minutes.
Now if we had more time, let's think about some things that we could do to take this further.
Well we just used simple UI elements like buttons and labels.
But you could use a framework like SpriteKit to create more imaginative buttons that have elements like gravity or physics associated with them.
We could also add MusicKit integration and have Apple music songs playing in the background during active gameplay.
Or we could read from sensors and change the speed of our game based on the user's movement.
Here are three talks from previous WWDCs that I highly recommend you check out.
Introduction to SpriteKit from 2013.
Introducing MusicKit from last year. And Creating Immersive Apps with Core Motion from last year as well.
Thank you so much. I'm going to welcome [inaudible name] on the stage to show you how to add additional screens to your app.
Good morning, everyone.
I hope you've enjoyed building the game with poops and unicorns.
My name is and I'm here to help you add some awesome features to your apps.
Along the way we'll learn about APIs and frameworks that are commonly used across iOS.
First, let's take a look at the features we want to add to our game.
We would like to introduce a leaderboard where we can see names and the points for each person who's played our game.
When we tap on a name, we want to see more information about that person.
As we build our app today, we'll focus on three main areas.
One is the data. Where should we store information about our users? How do we retrieve this data? Second is the user interface.
What does the leaderboard look like? What use should it have? And finally, we'll talk about the logic that's used for managing for passing data, and for doing other tasks within our apps.
If we break down our app into these three categories, then we would actually end up following a really popular architectural pattern known as the model-view-controller.
The model-view-controller represents the data in the model.
The UI is represented as the view.
And the controller is the logic that communicates with both the model and the view.
This pattern helps us group together similar tasks.
And it makes it easy for us to make changes to one part of our app without impacting the others.
In iOS, the controller can be represented as a subclass of the UI-view-controller class.
The view can be a subclass of the UI view class.
And the model can be a subclass of NSobject. When we build our app today, we will take a closer look at the different parts of the model-view-controller.
Let's now jump into a demo and build a model to store our data.
Here's the Disappearing Unicorns project that we made with Jessie.
Let me right click on the Disappearing Unicorns folder and say new file.
Select class which is what most iOS classes are.
I'll click next, and I'll pull my class data.
This will be a subclass of NSobject which is a good parent class for my data.
Let's hit next and create.
In this class, we want to store information about the player.
So let me use a shortcut to add some code I wrote before.
We have variables to store the name, points, rank, and image for each person. In addition to this, I've added some initializers to set up this data.
But we don't need to worry about those.
Let's go ahead and add one more class by right-clicking on the folder again and going to add files.
This is the game data class that I've written already.
Let's take a look at the methods that have been implemented in this class.
First, we have the save points for name method.
This is used to save the total game score for any given person.
Next we have the player data for rank method which will give us all the information about a given player at a certain rank.
And finally, we have a property to figure out the total number of people who played our game.
We will not look at the implementation details for these methods today.
What's important is to understand that we created a separate set of files to hold our data.
When you build your own apps, I would encourage you to think about your data as a separate entity and keep it independent of the user interface.
Just like how we've done here.
When it comes to actually saving and retrieving the data on the back end, we have a few different options.
One is to use core data. Core data is great for managing objects on the disc.
It provides you with solutions to validate, query, filter, and organize your objects.
If however your data is on a web server somewhere, then you could use NSURLSessions to download and upload the data. Another great option is to use CloudKit for storing data on the cloud.
You could even use a third-party cloud provider to manage your cloud data. Now that we've set up our data, let's move onto the next section where we build our user interface.
Here's what we want our leaderboard to look like.
I'll break this down into the different viewers on the screen.
On the top we have a navigation bar.
Below that is a table view which has rows which are known as table view cells.
Within each cell, we have an image view on the left, and some labels on the right to display text.
Besides the leaderboard, we also need to set up the details page. This one's pretty straightforward.
It has an image view and some labels.
So now that we know what views our UI is made up of, let's go back into another demo and actually set up this user interface.
I'll select the main storyboard which we built with Jesse. Here we have a single-view-controller which was used to manage the entire screen of content for the game.
Now we want to add more screens for displaying our leaderboard in the details view.
To do this, we can add another view controller from the object library.
I'll search for view controller.
Notice that there are a few different options for view controllers.
Since I want my leaderboard to look more like a table, I'll select the table-view-controller and bring it into my storyboard.
The table-view-controller automatically has a table view.
Let's select the table view and look at the Attributes Inspector on the right.
The content type here is set to dynamic prototypes.
I'll change this to static cells.
Static cells are great for displaying static data.
And these can be easily set up in the storyboard.
Now let's select a single cell and change its style from the Attributes Inspector to subtitle.
This gives me a title and a subtitle where I can display the name and the points on my leaderboard.
I also want to add an image to the left of the row.
To do this, I can simply type in the name of an image in the Attributes Inspector's image field here.
I have imported an image in my project just as a sample.
Let me add that.
Okay. So now my cell is all set up and we have a good outline for our leaderboard.
Let's go ahead and add the details UI. I'll go back into the object library, and this time we'll take a blank view controller and bring it into the storyboard.
Inside this view controller, we will add an image view.
Let me set the image from the Attributes Inspector.
Wait a minute. This is a little scaled.
Let me change the content mode from scale to aspect fit. Much better.
Now I'll go back to the object library and add some labels.
These are going to be used for storing the name.
I'll make a copy.
Next one is for the rank, and finally another label.
Going to make a copy. Another label for the points.
Okay. Now that both our view controllers are set up, there's one other thing to do. We need to tell our app to actually display this leaderboard or the details view after we do a certain action in the app.
Since we want the leaderboard to be displayed after we tap the leaderboard button. I'll create a connection between the leaderboard button and this table-view-controller.
Let's hold down the control key on the keyboard, and drag the mouse from the leaderboard button to the table-view-controller.
When I release, I see a menu with a few different options.
These are the different ways in which we can present the second view controller on top of the first one.
For now, I'll select the show option which is a commonly used segue for such apps.
Notice that a connection got created between the two view controllers.
This is known as a segue.
Now, I want to display the details-view-controller when I tap on the cell in the leaderboard.
So let's again hold down the control key and drag our mouse to the details-view-controller.
Select show one more time.
Now we are ready to run our app for the very first time.
Let's look at the simulator.
If I tap the leaderboard, I see a good mock-up for my leaderboard.
I can tap on the cell and we have our details view with more information.
This is looking good. But how do I go back to my leaderboard or the game? Let's go ahead and fix that.
To do this, I'll select the main view controller which had the game.
And then go to the editor menu in Xcode, select, embed in, navigation controller.
This adds a navigation controller to our app.
The navigation controller is a special type of view controller that is used for managing the back and forth transitions between our view controllers.
This also adds a navigation bar at the top of our view controllers. So from the Attributes Inspector, if I set a title to-- for my leaderboard, it will now show up in the navigation bar.
Now that we've added all the viewers that we needed to add for our UI.
Let me finish this up with adding an app icon to this app.
Let's go into our project navigator.
Select the blue folder that says assets.
And go to the app icon image set.
Now I have some icons that my designer created.
I'll select these and drop them into Xcode.
There's a specific way in which you need to create these icons. And we have guidelines on developer.apple.com.
This time when we run our app, I'll close this-- we will see an icon on the home screen.
Isn't it cute? Thank you.
Let's go back into the app.
And tap on the leaderboard.
This time we're able to go back and forth between all our views. This is great! Let's now- I'm glad you like that.
Let's now rotate our phone and see what happens.
Oh no. My labels are all clipped, and my image is too far to the left.
In order to make my layout look right-- let's put that back.
I'll use a technique known as Auto Layout.
Auto Layout is a set of rules that we define to tell our app how we want our views to be placed.
So each rule in Auto Layout is known as a constraint.
Now we'll add some constraints to this image view in our details-view-controller.
Look at the buttons at the bottom right of the storyboard.
We'll click on the align button, the one with two horizontal bars and say horizontally in container. Add one constraint. This tells our app that we want our image view to always be in the horizontal center.
I'll also click on the button to the next of this align button called add new constraints.
The top-most text box here represents the distance between my image view and its closest neighbor on the top.
So if I set this value, it will make sure that my image is at least, that my image is like ten points away from the nearest neighbor on the top. Which could be the edge of the screen too.
Let's also set the width and the height.
Now our image view is all set to use Auto Layout.
I'll quickly add similar constraints to all the labels.
We can do this in one go by selecting them altogether.
This time, if we run our app and rotate it, we should be able to see our view laid out properly.
There's an even easier way to validate our layout.
We can go to the Device Configuration pane at the bottom left of the storyboard.
And change the orientation here to landscape.
Now I can see my view in the landscape orientation.
And my image is looking, my image is in the center, and my labels are all seen on the same page.
You could even change the device from the Device Configuration pane to see how this would look on an iPad or a smaller phone.
With that, a UI is all set up.
Let's quickly recap what we learned in this session, section.
We started with a single-view-controller which had the-- which managed the entire screen for our game.
We learned that we can create multiple view controllers to display multiple screens of content.
If we do create multiple screens of content, then we need to tell iOS how to go from one view controller to another.
We do this by adding connections that are known as segues.
We created a table-view-controller which is great for displaying lists of data.
We also added it inside a navigation controller.
The navigation controller helped us go back and forth between the table view and the details page.
This pattern of using a table view along with the navigation controller is commonly seen across iOS apps.
Here are just some examples.
To learn more about view controllers, check out the documentation on developer.apple.com.
We also learned about Auto Layout which is a great technique for building good user interfaces for different screen sizes and different orientations.
I would recommend checking out these WWDC sessions to learn more about Auto Layout.
Finally, we can hook up our data model with our UI and write in the logic to bring everything together.
Let's take a look at another demo.
We need to save the score at the end of each game.
To do this, I will select the view controller that we wrote with Jessie.
In the game over method, I will call a method on my data model that we wrote before to save the points.
The-- this save points method takes two parameters.
One is the total points which we've already saved in the game points variable.
The second parameter is the name of the user who's playing the game.
So to recap, I've just added this little bit of code in our view controller that we created before.
The save points method on our game data model takes two parameters.
The first is the game points which we had already stored in a variable.
The second parameter is the name of the user who's playing the game.
In a real-world app, you would probably want to create a profile screen or a settings screen where the user can enter their own name.
But for the purposes of this demo, I'll just hardcode this to my own name.
Now that we've saved the score, we need to write some code to actually display the right scores and the names on the leaderboard.
So let's go ahead and create another class by right-clicking on the unicorn's folder and going to new file.
A class again.
This will be a subclass of the UI table-view-controller.
Remember when we created the leaderboard on our storyboard? It was a table-view-controller, so I use a table-view-controller class again to put in some code for that leaderboard.
Let's call it the leaderboard-view-controller.
Hit next. And create.
This already has some code that has been generated for us by Xcode.
These are methods that developers find useful when building their own table-view-controllers.
We will implement two of these methods.
First is a table view number of rows in sections.
This method is asking us for the total number of rows that we want to display in our table view.
In our case, the total number of rows will be the same as the total number of players that have played the game. And we can get this information again from our data model.
So the number of players variable will give us the total number of rows.
The second method that we need to implement is the cell at index path method.
This method is called every time a cell needs to be displayed on our leaderboard.
The index path argument tells us the row number for the cell that will be displayed.
And in here, we're expected to configure the cell just like the comment says.
So let me pull in some code to set up this cell. We are using our game data class again.
And the index paths row will tell us the rank of the player.
Since we want to display the players in ascending order.
Once we have the player rank, we can send it to the player data method on our game data class and get more information about that player.
Using this information, we can set up our cell.
The text label is the title.
The detail text label is the subtitle.
And the image view is the image that will have the photo. Now instead of creating this game data instance twice, I'm just going to put it at the top of the class so it can be reused.
Let me also delete the number of sections method that was added for us by default, because we don't need this today.
Now that we have written the code for the leaderboard, let's open the main storyboard and the Assistant Editor on the right.
I'll rotate the specs so we can see it properly.
We need to tell Xcode that the code for our leaderboard here is written in the class that we just created.
To do this, I'll select the view controller for the leaderboard.
Go to the Identity Inspector, and change the class name to leaderboard-view-controller.
After this, I'll select the table view in the storyboard.
Go to the attributes Inspector and change the content type to dynamic prototypes.
This means that the cells are now being created dynamically in the code that we wrote.
We will also select a single cell.
And in the identifier section in the Attributes Inspector, I'll copy over the reuse identifier from the cell index path method in my class.
By doing this, I'm saying that I'm willing to reuse the cells in my table view.
This will help improve the performance of my table view.
Finally, we've written the code for this leaderboard class. We still need to write code for our details-view-controller.
Luckily, I've already added some code that we'll import into our project.
This is the details-view-controller class.
Let's jump to it from our jump bar.
Here we have some IBOutlets for the different views in our details-view-controller.
Remember when we wrote the game, we connected these IBOutlets to the views on the storyboard.
But we're not able to do that right now.
This is because we haven't told Xcode that the code for this view controller is right here.
Let's do that again by going to the Identity Inspector and changing the class name to details-view-controller.
Now we can connect the IBOutlets easily.
By doing this, we can set the views from our code like I've done in the view load method here.
Let me hide the main storyboard for a moment. We also have a player info variable here. And we are using that player information to set up our views.
You might be wondering that we didn't really send this player information anywhere.
So how do we get all this data? We actually need to ask our leaderboard about the person whose name was tapped.
So we'll go back in the leaderboard scoreboard and figure out which person we need to display more information about.
I'll jump to the leaderboard-view-controller.
At the bottom of this class, we have a method that was written for us by Xcode called the prepare-for-segue method.
This gets called while we're transitioning between one view controller and another.
It will be called for us as soon as we tap on a cell in our table-view-controller.
So in here, I will get more information about the player based on the rank again. And I can figure out the rank because there is a property on the table view called index path for selected row. This tells me the row number for the cell that was selected.
We also get a segue parameter in this method. Remember how segues connect two view controllers? So the segue's destination property will tell me which view controller we're navigating towards.
Once we have an instance of the details-view-controller which is the one we're going towards, then we can set the player info with the details we have.
Finally, we are ready to run our app one last time and see how everything comes together.
So now we'll play the game. And we go to the leaderboard, and we can see all the information coming in from our data model.
I made only one point, so I'm at the end.
Let me see what my rank is.
Rank eleven, not too bad. At least my app is all set up.
Now that we've built our app, let's take a look at some next steps.
Before you release your apps, it's important to test them.
The exit test framework can be used to write unit tests. You should also check out the App Store review guidelines.
These are meant for creating a good experience for users and developers alike.
At some point, you'd need to enroll in the Apple Developer Program.
This will help you create the certificates and profiles that you need to distribute your apps.
Finally, submit your apps for review.
Once they're approved, go tell your friends and family and the whole world. That you've built an app.
To learn more about these next steps, check out the resources section for this session on your WWDC Apps.
To summarize, I would encourage you to explore Xcode. It has many tools and templates that make iOS development really easy.
You can easily set up the user interface using the storyboard.
Try some views and see what your app might look like.
Think about what data you might need, and how you would store it.
It's important to create good user experiences for all devices.
This might mean optimizing performance for older devices or taking care of different screen sizes.
Follow the guidelines and best practices to make a good app. If you've done all this, then you're officially an iOS app developer.
Congratulations! And have a great WWDC.
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