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In the last lesson, we got our skeleton project off of GitHub and we managed to link up an IBAction
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with a single button on our Main.storyboard and that's the first button, this red button here, so
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that whenever it's pressed the words "I got pressed" get printed into the debug console.
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We're now pretty certain that our IBAction is linked to that red button and we can trigger some bit
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of functionality to happen when we press on the button.
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Now, of course, the actual functionality we want is to make it play a Xylophone note, but we don't know
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how to do that yet.
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Now, I could simply tell you, "Well, here's step A,
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this is what you do," but it doesn't answer the question of, "Well, how did I know how to do it?"
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Instead, I want to show you how we can use the Application Programming Interface Documentation which
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is quite a mouthful, but essentially, just refers to the components that Apple have already built into
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iOS that we can simply tap into and use, because Application Programming Interface takes like a whole
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second to say
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that people often refer to it as the API.
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So the API for your TV would be something like turning the volume up and down or switching the TV on
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and off or changing the channel number.
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So the API docs for your TV would then be the instruction manual which you probably throw away.
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But luckily for us, the Apple API Docs are hosted online and you can find them at developer.apple.com
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and then in documentation.
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So this is basically the instruction manual for programming
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iOS apps. Nut just like most manuals, they're so information-dense.
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And if you dig into each of these, you'll find that they have endless links after links after links and
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it's really hard figuring out exactly what you need to do from the documentation.
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Just like when my mom has a problem with her TV, she'll always call up tech support which is, basically,
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me, instead of reading the actual instruction manual for her TV.
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Well, programmers also don't usually start with the API Documentation,
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instead, we tend to use the programmer's tech support which is StackOverflow. Now StackOverflow is basically
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a Q-and-A website like Yahoo Answers or Quora,
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but for people who code. So let's say I had a question and because programmers are programmers, there
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are some crazy questions on here and some brilliant answers.
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If you ever wanted to know what is the most efficient way of pairing socks from a pile, well, you could
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search on StackOverflow and you'll see that somebody has asked this question six years ago with three
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thousand upvotes.
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That was a really popular question and we have a bunch of answers, in fact, two whole pages of answers
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here. And the top answer got a lot of upvotes, as well as the checkmark which means that the original
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person who asked the question has accepted this as the answer.
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So if you ever want to know how to sort your socks in the fastest way possible, well, apparently, you could
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use a hashing algorithm. Now because there are literally millions of things that you can make your iPhone
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app do,
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it will be impossible to remember all the names of those things that you need to use or the exact code
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that you would need to write,
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even things like how to change an image in an image view. You don't need to memorize the code ImageView.image.
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You could just look it up. And in the answer,
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people often provide a code snippet where they show you the answer or how to achieve what you want to
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do.
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So in this case, here's your ImageViewOutlet.image
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= your Image, and then we would be able to set the image view. Whenever you want to solve a
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problem in programming or when you want your code to do something specific,
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then I recommend following this five-step process which we're going to go through by trying to figure
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out how we can get our app to play sound.
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Step 1 involves Google.
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Step 2 involves going to StackOverflow.
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Step 3,
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implementing the code that you find there.
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Step 4, looking up what the code means in the docs.
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And step 5, customizing the code for your needs.
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And we're gonna go through this step by step.
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So let's start with the first one.
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Now, ask any experienced programmer and they will tell you that a large part of getting good at programming
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involves getting good at Googling. And two people with the same resources, say, a computer that's connected
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to the internet don't always end up with the same solutions.
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And some people might not even find a solution.
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So when you're doing mobile app programming, I recommend following this search structure.
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So, first, what I want my app to do.
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Secondly, which programming language am I using.
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And third,
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which resource do I want to come up.
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In our case, our search query will look something like this, Play sound using Swift on StackOverflow.
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So let's try it out. In Google,
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I'm gonna put in those exact search terms "play sound Swift using stackoverflow," and what we're looking
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for is a website that starts out with stackoverflow.com.
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So we're basically leveraging the power of Google's search engine to find the most relevant result on
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StackOverflow.
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Now you saw that we could also just search for our query in StackOverflow itself, but I find that Google
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is far better at search algorithms than any other company.
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Google looks at how often a search term leads to a click of a link, and then whether if the person stays
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there, which means that they found the right resource for that search term, or whether if they head back
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which means that they didn't find the right one and they have to look through the list.
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So step one, basically, ensures that you get a more relevant result.
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And once we found the StackOverflow answer that seems to most closely match what we want to do, in this
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case, the question is how to play a sound using Swift?
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That sounds pretty close to what we want to achieve, right?
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Well, then we can go ahead and head over to StackOverflow and take a look at the question and answer
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there.
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This takes us onto step two, exploring the question-answer
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on StackOverflow itself. And in this case, it's a good idea to take a look at the question to assess
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whether if your own query is similar to what this person is asking for. In this case, they want to play
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a sound using Swift and they had some code that worked previously, but it doesn't work in newer versions
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of Swift.
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So they want to know how do you do it now.
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So if we scroll down, you can see that there are total of 13 answers that have been provided. And people
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will often compete for highly voted questions because it means that their answers will get more exposure
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and they're more likely to collect reputation points.
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So every time you upvote somebody's answer or accept their answer as the correct answer, they get
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reputation points which you can see down here.
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And this is kind of like a game fight system to incentivize programmers to help each other, so that they
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can gain reputation. And as you get better in your skills, it's a good idea to pass it forward, and help
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people with what you know. And, also, when you go to job interviews as a programmer, by mentioning a really
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high reputation on StackOverflow,
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it also counts for a lot.
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So it helps to help others.
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Now, over here in the accepted answer, so the one with the green tick, you can see that they've provided
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code snippets for how to implement this functionality of playing sound using various different versions
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of Swift.
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So it's Swift 2.3, 3, and 4. 
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I recommend looking for the latest version and anything from Swift 4 onward, so Swift 4, 
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5.2.
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These are all pretty similar.
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As long as you see something that is Swift 4 or Plus, then you should be all right
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implementing the code. The order of the answers are presented in a specific way.
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The first one that you will see is often the accepted answer.
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So the one with the green tick on it.
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And if you scroll down, you'll see the answers ordered by the number of upvotes,
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at least this is the default order system. Now, because everything in development and programming moves
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on so quickly,
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just because the person asking the question accepted this answer back in, say, 2013, it doesn't mean that
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it's still the best answer.
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I always recommend students to take a look, not just at the top answer, but the top three to see if there's
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something that's more relevant to today.
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So now that we've found our answer on StackOverflow, it's time to go to step 3 and implement the sample
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code in our app.
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In this case, I'm actually going to use the top answer.
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Not only was it accepted, but it's also got a whole bunch of different versions and it seems to be the
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most compatible with where we are today.
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Let's try and use this code snippet to implement it in our code and try to get our app to be able to
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play sound.
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So the first line of code I see here is this
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import AVFoundation.
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I'm going to put that into our project just below where we are importing UIKit.
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I'm going to import the AVFoundation module.
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Now, these modules are essentially the libraries of code that Apple is written to allow us to interact
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with different parts of the hardware and to perform different tasks.
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So in this case, the AVFoundation refers to the audiovisual foundational module.
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Now that we've added the capability of interacting with the audio hardware, which is what this line does,
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it's time to actually set up our audio player.
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Notice how here we're creating a variable code player
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and we're setting it to be a AVAudioPlayer
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in our code.
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So we're gonna create a variable code player and then we're going to add a colon to specify the data
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type of our player which is gonna be AVAudioPlayer,
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and then we add a question mark at the end.
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Now, we're going to ignore this for now.
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I'm going to explain it in a huge amount of detail later on. But for now, let's focus on trying to get
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our sound playing ability to work first.
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The next thing I'm going to do is I'm actually just going to copy this entire thing wholesale,
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the rest of the code that's in the code snippet, and simply paste it into our project just above the
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last closing brace,
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so right about here.
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Now, once I pasted it in here,
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now we're going to have to do a little bit of modification because we don't actually have a resource
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code sound name,
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and with the extension of mp3 because we have sounds that are named like this C.wave, D.wave.
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So we have to change these.
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So I'm going to change this to a capital C, which looks exactly the same as the sound file, and I'm going
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to change the extension to wave which is W-A-V,
not W-A-V-E.
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So now I've modified the sample code in the StackOverflow code snippet to work with our resource
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and I'm going to leave everything else as it is. But because this play sound lists in a separate block of
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code, I'm going to trigger it inside all keyPressed IBAction. So I'm going to delete that print statement
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and instead, call this playSound functionality, so that when we press the red key, this block gets triggered
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and it looks for this thing called playSound. It finds it right here, and then it executes all the code
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in this block.
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So let's hit run and see if it works. All right,
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so here's my app and I'm gonna press on the top button, and you can hear that a sound is being played.
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So now that we've achieved our first three steps, we've managed to implement the solution we found from
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StackOverflow.
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We're now ready to head over to step four which is to look at the Apple API Docs to understand what
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the code does. I'm firstly going to delete all of the existing comments
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that the person who provided the solution has put in there so that we only have the code, and then
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I'm gonna head over to the API Documentation, and you can find that by heading over to
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developerapple.com/documentation.
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I'm going to search for that thing that we imported which was called AVFoundation to see what it does.
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And the first result is the AVFoundation module that comes up. And this, as you can see, allows us to
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work with audiovisual assets.
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So, for example, our sound file to control cameras, to process audio, and to configure audio interactions.
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So it seems to do a lot of things. And you can see that the documentation is split into different topics:
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Playback and Editing, Media capture, Audio, et cetera. If we read through this, you can see that there's one part
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that allows us to play, record, mix, and process audio. Playing or audio is pretty much what we wanted to
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do, right?
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So if we click through on this link, you can see that it gives you more details on how to play sound
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using AVFoundation.
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And it says that for playback of a single track, use AVAudioPlayer. And if we take a look at our code,
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well, the AVAudioPlayer is exactly what we're using to play our sound.
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Now, if we move down in our code, we can see that we've got this thing called a Bundle.
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Now what exactly is a bundle?
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So let's try and understand that by looking inside the documentation and searching for a Bundle.
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Now if you click on the first link with the capital B for Bundle, then you can see that it's simply a
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representation of the code and resources stored on the disk. And in our case, we're using the main Bundle
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to locate our sound file resource. So if we ignore all the sort of programming keywords in pink, you can
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see that we're essentially creating this constant code URL which is looking for a resource code
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C.wave in all resources,
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so the disk area allocated for our app. And then the next thing in our code that we're using, the next
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sort of word that's really unfamiliar, is the AVAudiosession.
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I'm going to copy this and look for it inside the docs by, again, going to the search bar and typing it.
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And once we're here, then we're going to look for this thing called setCategory. What does setCategory actually do?
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On this page AVAudiosession, I'm going to hit command F to find this set category. And if you
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look through, you'll see where it tells us all about it.
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So here, we could click through to this link and learn more about this setCategory and what it does.
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Here we have a bit of discussion on how it works and you can find out that there's actually a whole
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bunch of categories that we might want to use.
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And the one that we're using is something called playback.
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So on this page, we can see this ambient which means that the sound playback is nonprimary,
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so your app can be used successfully with the sound turned off.
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So then there's other types like solo ambient or record playback.
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And this is one that we're using which is saying that the category for playing recorded music or other
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sounds are central to the successful use of your app. Given that it's a musical app, then playing all sounds,
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playing those notes is pretty central to the success of our app.
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It's not just like background music in a game with some sound effects.
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It's actually really important for that sound to come through.
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So by setting in that category, even if the user had their phone on silent, we will still be able to get
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our sound played because we're saying it is that important.
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And if you read through the documentation, the entire documentation on AVAaudioSession, which is what
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I did, then you'll find that there's this paragraph that explains to you that when in iOS, when the device
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is locked, the apps audio is silenced. In iOS setting, the Ring/Silent switch to silent, silences any
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audio being played by the app.
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So this is the default audio session. And we had to use this line of code to change that default audio
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session to a new category so that we can actually get our playback happening even if the phone is in
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silent mode.
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So notice how we're always researching the parts of the code that are sort of purple in color.
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Well, that's because by the end of the course, you will know full well what each of the pink parts do
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because these are these swift programming concepts. But you won't know all of the purple parts because
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these come from Apple's Application Programming Interface Documentation.
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So there are a myriad of things that you can do in there, anywhere from playing video to recording sound,
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and it's not possible to cover all of the things that you can do.
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But once you've understood how the programming works and you know how to search and find the answers
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to your problems, then you'll be able to research through the code just as we're doing right now. If you
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continue through this process of researching what each of these things do by using the documentation
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from Apple, then you'll get a pretty good idea of what our code is doing right here.
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We're basically grabbing hold of this C.wav file in our app resources right here, and then we're
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making sure that our sound gets played even if the phone is on silent.
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And then we tell our audio player that this is the file that we want to play C.wav,
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and then we actually play it. And if there were any errors, then we actually catch those areas and print
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it out. Now, this is a good time for a quick tip.
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Now, when you search for things in the Apple Developer Documentation, you get the full documentation and
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it is large.
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Very often when I'm using something new that I've never come across before, I tend to try and read the
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entire page on it and look through the links and try to get a overview of what I'm doing with my code.
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But when you're just trying to look up things quickly to see what they do,
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you can also simply hold down the option key on your keyboard and click on various things in your code.
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So as soon as I've got my option key held down, I've got this crosshair that shows up,
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and now if I hover over things such as my AVAudioPlayer or my Bundle, or AVudioSession,
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so basically anything that's not programming,
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so not the pink words which are to do with swift programming keywords, but the purple parts which come
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from Apple's APIs, then we can click on it and it will show us the quick documentation.
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So it's kind of like a shortened version of this.
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It only contains the top part. And you can get a quick idea about what each part does or take a look
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at it in detail in the developer docs.
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So that's just a neat trick for you.
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Now, we're finally ready to move on to the last step which is to customize your code. Now reading the
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documentation can be quite a long and laborious process. But once you've implemented the code and gotten
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it to work, then the documentation can be really helpful to help you figure out what each of these moving
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parts are doing and what their roles are.
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Once you've more or less understood what each line of code is, therefore, well, then it's time to make
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it your own.
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Because not everything that's in the code is necessary and the person who wrote the highest upvoted
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answer is not Steve Jobs, right?
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So they might also be wrong or they might be doing things that you don't actually need.
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And this step is probably the hardest part yet because it requires a little bit more knowledge of Swift
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programming and you'll be able to do this yourself once you've finished the course.
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But for now, I'm going to vastly simplify the code, so that we deal with the harder programming concepts
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after we've mastered the foundation parts.
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If you open up the README file here, I want you to copy all the code that's inside the replacement
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code, and go ahead and copy it and replace everything that's currently inside your ViewController with
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this new code.
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Now this, of course, relies on the fact that your IBAction was indeed called keyPressrf and it was spelled
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exactly the same way.
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Be sure to head into the IBAction and right-click on your button just to make sure that that is exactly
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the same as this,
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so that when you run your app, it doesn't crash, and we're going to simplify all of the code that we had
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before
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down to just these few lines.
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Now, it's much simpler.
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But we've gotten a little bit less functionality than before,
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but it's fine for our needs.
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We're still using the AVFoundation library from Apple.
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We're still creating a new AVAudioPlayer, and then we're setting
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our URL to be the location of our C.wav sound file in our project, and then we put this file
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into our player just like loading up our CD player with a CD.
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And finally, we tell it to play the sound.
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Now, remember, because we took away the parts which allow our sound to be played when the phone is on
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silent,
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if you run this app right now and your phone is on silent on your physical device, then it will not make
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a sound.
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But as long as you switch it back onto normal, then it will be fine. And this is all of the code that
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we got from our searching and our documentation reading, and we now have code that we understand, as well
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as having implemented for our purposes.
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Now, all that's left to do is to understand more of the Swift programming concepts behind this code, for
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example, functions and what it's doing in our code. For all of that and more, I'll see you on the next lesson.