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All right.
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So first things first, you should have cloned the starting project from the GitHub repository FlashChat
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iOS 13, and we're going to clone it like you have done before many, many times.
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So once you've cloned it, you should end up with a file that looks like this.
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And if you go ahead and expand the folders, then you'll see that we've got a Main.storyboard that's already
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been set up.
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And in this app, we've got a little bit more of a complex setup.
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We've got four screens and this first screen is the welcome screen,
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then we've got a registration screen, a login screen,
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and finally, the actual chat screen.
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So notice how we're using a lot of custom assets in here.
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For example, the way that we're able to get these shadows and shapes around these text fields, the email
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and password text fields is by using some custom assets that we've added in here.
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So these have their custom shadows and shapes and we've basically just used these as an Image view, so
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that we can give our app some custom design and make it look beautiful.
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Now, in addition, we've got some colors that are going to be the brand colors for our app.
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So we've defined these colors over here. And then we've given them a name so that we'll be able to identify
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it in our app.
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And we've also got some other images, such as the app icons and the avatars that we'll be using in the
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app.
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So heading back over to the Main.storyboard, you'll notice that if you go into Assistant mode that
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we've already linked up some of these IBOutlets and IBActions.
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So for example, over here on the welcome screen, we've got the titleLabel that's been linked up, and then
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over here on the registration and login screens, we've got these text fields already linked up and the
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IBActions for the buttons.
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Now, if you don't see the files that are associated with these design files automatically showing up
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when you go to the assistant view, then it might just be that you have to click on automatic and select
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it manually which is a little bit ironic given that it's called automatic.
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But essentially, the reason why these are paired up if you remember is because we've actually linked
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it in the storyboard file, so when we've selected each of these screens and we've created these new view
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controllers, we've added it inside here as the custom class that's going to control the screen.
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And we've done that for each of these screens, so ChatViewController is linked
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to ChatViewController.swift, the login view controller screen is linked to the LoginViewController.swift,
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et cetera. But sometimes Xcode is a little bit weird and it shows you this file which is actually
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the header file, which is not what we want, and instead you want to click on Automatic and select the
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Swift File like this.
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So let's go ahead and close down our assistant and let's head back to our Main.storyboard.
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So notice that most of the components that have been added here are things that you've already seen
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before,
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so labels, buttons, text views, image views, but this we've yet to use.
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So this is what's called a table view and you can get hold of it by simply going to the Object library
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and searching for a table view. And you can read through this,
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but basically, it's just a way for us to be able to display data in a list.
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So on Android, it's called a list view and it's probably a little bit better of a description,
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rather than table view.
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But if you have an iPhone, then you've already seen table views.
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If you think about your mail app, this is a bog-standard table view without any modifications.
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And even if you think about the chat app, this is actually still based on a table view because it's vertically
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stacked cells and each of these are just simply customized to look a little bit more pretty than the
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standard table view, and we're gonna be doing this later on ourselves, as well creating these custom views
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in our messaging app. So if in the future, you need a table view or you need the functionality of this
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kind of vertically scrolling and stacked components, you'll know to get it from the object library. 
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Drag it on and link it up as an outlet as you would for any other component on the Main.storyboard.
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So the other thing that you might have noticed when you've opened up this app is that we've got a couple
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of warnings here. And they're telling us that there's a couple of view controllers on our Main.toryboard
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which is unreachable because it has no entry points.
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So what does that mean?
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Well, notice how we've got these four screens. We've got this arrow which determines where the app is
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going to start out which screen it's going to show first.
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And you can drag this around or you can simply select the View Controller and click Is Initial View
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Controller.
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It does exactly the same thing.
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I find it easier to just visually just drag that arrow around. But you can see that if this is the entry
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point, this is the first screen that the user sees.
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Then in order to get to some of these other screens, we're going to need some segue ways, right?
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And at the moment, there are no segues because I've left it for you to set up.
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So I want you to see if you remember how to set up segues and I want you to set up a segue between
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the RegisterViewController and the ChatViewController,
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so from this screen to this screen. And then another one between the LoginViewController and the
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ChatViewController,
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so from the screen to the screen. Because remember, once the user successfully registers all logs in which
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take them directly to the ChatViewController.
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So pause the video and see if you can complete that challenge.
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All right.
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So this shouldn't be too hard. 
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Remember, firstly, we have to select the entire view controller, and you can either click and drag like this, or
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the easiest way is actually just to click on this little yellow icon up here which does the same thing.
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So, now from this point, from the RegisterViewController, we're going to make a link or a segue to the
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CharViewController.
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So I'm going to hold down the control key on my keyboard, click from here and drag it over to this screen,
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and then go ahead and let go.
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And now I've created a segue and I'm going to choose a bog standard show segue as we have done many,
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many times before.
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And then I'm gonna do the same thing for our LoginViewController, and now we have two segue set up.
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So if you're at all confused about this, then be sure to head back to previous modules or search in the
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course for segues,
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because we've covered this in detail before. So I'm not going to waste too much time talking about it
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again here.
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Now, the type of segue that I haven't shown you before is a much simpler type of segway because these
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segue actually connect a view controller to another view controller. So they have to be triggered
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manually and we do that using the identifier.
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So you've seen this before as well. But there's another type of segue which is much simpler.
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We can actually select the register button, hold down the control key on the keyboard, click and drag
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from it to the register screen.
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So this way, what we're saying is that we should show the RegisterViewController when the user taps
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on the register button. And indeed, if you right-click on this button now, you can see that there is now
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a triggered segue set up so, that whenever this button is tapped, it goes straight to 
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the RegisterViewController.
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So let's go ahead and do the same thing for the login screen as well.
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And now if we go ahead and run our app, then you'll see that when I click on register, it goes to the register
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screen,
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and when I click on login, it goes on to the login screen.
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Now, notice that we're getting what's called a modal transition.
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So this is a screen that slides up from the bottom and covers the one that's behind.
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Now, this is not quite the behavior that we want because what we actually want to do is to have a navigation
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stack,
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so a way to be able to replace the previous screen with the next screen. Because this way will end up
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with a navigation bar and will end up with a back button which allows us to go easily back and forth
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between the welcome screen and each of these register or login screen.
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Now, how do we do this?
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Well, it's pretty simple.
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We select the first view controller.
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So this is what we would call the route view controller, it's the one that we started from.
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And we select it again using that yellow button. We go to Editor and then Embed In, and then we select Navigation
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Controller.
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And notice how
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as soon as I do that, you'll see that all of the downstream view controllers get a navigation bar added
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in completely for free.
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So we haven't done anything to create these other than embed the route view controller into a navigation
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controller stack.
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So, now each of these screens have a back button and the screen has a top navigation bar.
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And if we run our app again, you'll see that we're able to navigate back and forth and this is the same
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behavior that you see in a lot of apps like the settings app on your iPhone or the mail app.
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And this is a really common way of replacing screens with other screens. And creating the navigation
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for an app that has lots of screens like we have here.
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So Navigation Stack is a little bit like a stack of pancakes.
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So I know you guys are missing the food analogies.
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So this is it.
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It's coming in right now.
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Here we've got a stack of three pancakes, right?
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And in order for me to be able to eat the last pancake, I can't really get to it unless I remove the
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top two.
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So the that the Navigation stack works is that for every new screen that's presented, they're stacked
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on top one another like a stack of pancakes.
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And in order to get to the bottom one, we have to actually take these off which means these pancakes
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at the top will get destroyed and dismissed, or eaten, or deallocated memory, whichever term you prefer,
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and that way, we can actually get to the very, very bottom, pancake or in our case that would be the root
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view controller which is this screen right here.
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So, now effectively what I've got is the user will enter on the welcome screen, and then when they click
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on the register button, that is going to take them to the register screen. When they click on the
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login button,
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it's gonna take them to the login screen.
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And then once they've actually been successful in registering, then do we actually trigger the segue
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to the table view.
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And once they've been successful in logging in, do we take them to the chat view as well.
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So these segues are unconditional, right?
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It doesn't matter what they've done or if they're authenticated.
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We don't actually care. As long as they press that button,
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we take them straight to the screen.
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But these segues down here, actually depend on something.
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It depends on whether if they've successfully registered or successfully logged in before we actually
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trigger these segues.
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So that's why we've got two different types of segues. And our navigation stack basically allows
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the user to navigate between these screens in case they've made the wrong decision, say, they've clicked
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on the register, but actually they've already registered, so they actually need the login,
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et cetera.
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So that's a really common sort of pattern that you'll see.
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And this is the reason why we're getting some warnings about these two segues.
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So you can see when I click here on the warnings, it's highlighting this segue and this segue, but not
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any of these, because these don't need an identifier, they are automatically going to be triggered from
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the buttons.
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So these ones need an identifier, so that we can trigger it from our code.
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So the first one I'm going to call RegisterToChat.
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So this is from the register screen to the chat screen. And make sure that you've spelled it exactly the
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same way as I've got it here,
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so that further down the line, we won't end up with any problem of mismatch.
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So let's hit enter on that one. You'll see one of the warnings disappear.
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And then this one, this is going to be called LoginToChat. And notice how login, the "I," I've kept lowercase.
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So, again, make sure that you've got exactly the same spelling as I've got here.
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So, now when we hit enter and activate that, then we should be able to clear our warnings.
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So, now if you hit command B to rebuild our app and refresh those warnings, then all of the ones that
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shouldn't be there anymore should get cleared.
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And we've now gotten to our starting point and we're ready to create some functionality in our app.
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In the next lesson,
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we're going to be adding some animation to our title here, the FlashChat title. And in order to do that,
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we're going to be learning about Swift loops.
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So all of that and more, I'll see you on the next lesson.