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So the first thing we're gonna do is, of course, clone our starting project which you can find in the
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course resources link.
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And for those of you guys who want practice creating the User Interface and doing the Auto Layout, then
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there's, of course, the alternative that you can work on.
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In other words, you've got two stops to choose from, one stub with the screen already designed for you,
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so you can focus on Swift programming and one where you can practice recreating this design on your
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own.
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Now, the goal of this lesson is the setup our project and link up our storyboard to the view controller.
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That way we can make our buttons interactive and show different questions on the screen.
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So here's our Main.storyboard.
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And the first thing we have in our stack is a label, and then we have a True button and a False button.
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And finally, at the very bottom, we've got a progress view which is styled as a Progress View bar.
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So now all we have to do is open up the assistant editor and link up our code with our design.
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So firstly, I'm going to create an IBOutlet from my Question label as well as my progress view, and I'm
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going to call the top one questionLabel, and I'm going to call my progress view, simply a progressBar.
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All right.
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So we now have our two IBOutlets, our questionLabel and our progressBar.
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I'm going to create two more IBOutlets for each of the buttons.
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So one from the True button which I'm just gonna call trueButton and then another one from my False
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button which is going to be called falseButton.
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All right.
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So everything on screen now has an outlet.
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So the final thing to do is to add an IBAction which gets triggered when either the True or the False
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button gets pressed.
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So let's start from the true button.
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And I'm going to call this action answerButtonPressed and, of course, I'm going to change the type of
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my sender to a UI button, and then hit Connect.
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And now I'm going to click back and drag it back to the False button as well so that they're both connected.
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All right.
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So now we're done with all of our linking, so we can head straight into the ViewController.swift
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and see what we have done.
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So we have this block of code which will be triggered whenever either of the answer buttons are pressed
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and we can change everything on the screen through these four outlets.
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Currently, when we run our app or that we see in our question label is just the words Question Text because
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that's what we added here as the starting sort of place holder values.
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But we want to replace that text with an actual question.
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And I want to pose this as a challenge to you. Without touching anything in the Main.storyboard, namely
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the Attribute
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Inspector, can you write some code so that even though our question label starts out in our Main.storyboard
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saying Question Text, as soon as the app runs, make it actually show a question?
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So in this case, it says, "Four + Two is equal to Six," and then the user would have to choose whether
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if that's True or False.
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So pause the video and try to complete that challenge and have a think about which part of your code gets
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triggered when the app is first loaded up.
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All right,
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so here's the solution.
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We have this function called viewDidLoad and already in the comments of our template, Apple already
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is hinting at us that this is the place where we do any additional setup after loading the view.
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This is the block of code that we can affect if we want something to happen as soon as the view loads
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up or as soon as the app appears on screen.
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So what we want to happen here is we want to tap into the questionLabel and change its text property
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to, say, "Four plus Two is equal to Six."
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Now, if we run our app, then you can see that even though our Main.storyboard starts out with Question
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Text, as soon as the view loads up, it says, "Four + Two is equal to Six."
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Brilliant.
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Now, a single question quiz app is not most people's idea of fun, so let's jazz it up with some more questions.
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And to do that, I'm going to create a array.
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So right up here just below my IBOutlets, I'm going to create a constant code quiz and it's going to
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be an array that stores three questions
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All right.
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So now I have a array of strings and I've got three items in here which are separated by commas.
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And now I can use this array to show my questions in my questionLabel, instead of having these bits
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of text floating around.
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So here's another challenge for you. Make the question label display
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the first question from our quiz array.
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So the end outcome should be the same.
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We should still see the same question on the screen, but we can no longer use it directly like so.
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Pause the video and review what you learn about arrays to see if you can complete this challenge.
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All right.
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So in order to complete this challenge, we have to use our quiz array. And in order to get the first question
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out of our quiz, we can simply add a set of square brackets and pick out the one at zero position which
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is, of course, the first question in our array.
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Now, when we run our app, we get exactly the same as before, but now we're using some more dynamic code,
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rather than just setting it manually.
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Now, even though we've got three questions, we can't actually progress through them yet.
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And ideally, we'd really like our answerButtonPressed function to be the trigger that changes the
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questionLabeled.text.
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So in order to do this, we first need a variable to keep track of which question the user is currently
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reading.
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Let's call it questionNumber and we'll start it out with zero because that would match with all zero
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position which is the first question.
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So now we can change this zero from using a hardcoded zero to using our questionNumber. So, again, if
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you run your app at this stage, it will work exactly the same as before,
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but we've now made our code even more dynamic and we can now increase our question number by one every
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time a answerButton gets pressed. So we can either write questionNumber equals the current value of
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question number plus 1 or,
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of course, we can use the shortened version that we've seen before which is just += 1.
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So here's a question for you to play computer.
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What do you think would happen if we ran the app at this stage?
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So don't run it,
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just think about what might happen.
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Do you think it will change the quiz text
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every time we press the answer button because we're increasing the questionNumber?
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Well, let's check it out.
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So when we press the True or False buttons, notice that nothing is changing about our 
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questionLabel.text.
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So what's the reason here?
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Well, the only place where we're changing that questionLabel.text is, of course, inside of viewDidLoad
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block which only gets triggered once the first time the view loads up.
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So in order for this to keep changing, we actually need this line of code to be triggered again.
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So why don't we go ahead and create a function that captures this functionality and we'll call it update UI
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because in all likelihood, we're probably going to need this functionality a few times.
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So if I command X to cut it from there and paste it inside update UI, every single time I need that functionality
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I can now call my function Update UI.
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So I need the UI to update when the view loads up, but also after I've increased the question number.
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So now I've got my code in two places all triggering the same function which is to update the question
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label based on the current question number.
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So now if we run our app,
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you can see that when we press on this button, it will increase and go through our quiz questions.
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Now, of course, if you go beyond the third question, your app will crash.
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And this is, of course, because we only have three questions. If you're requesting for the fourth one, that
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doesn't exist,
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well, then we get a index out of range error. So our index which is currently number three is out of the
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range of our quiz because it only has 0, 1, and 2.
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And here's a quick way of seeing what's actually going on.
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Notice how when your app crashes, it highlights to you the line where the fatal error, which is really
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dramatic for Xcode to say, but this is where the fatal error occurred
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and that's what killed your app.
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Now, when your app crashes, you will see the debug console pop up, and you will see the useful messages,
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usually at the top of the debug console. So if you ever are in doubt, just scroll to the very top and
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read what it says.
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Now, the other thing you can do is you can expand this little dropdown list here, and you can see the
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value of some of the variables we have created.
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So currently at this point in time, when the app crashed,
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my questionNumber variable was equal to 3.
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Now, that means that I tried to pull out the quiz value at index 3, 0, 1, 2. Of course, 3 doesn't exist.
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So that's another way of helping you to debug and figure out what's wrong with your app.
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But there's no problems here.
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We expected that to happen.
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So let's go ahead and just stop our app. And in the next lesson, we're going to figure out how to not
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just solve this but also how to check the user's answer and see if they got the answer right.
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For all of that and more, I'll see you on the next lesson.