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Now that we're all skilled up on functions with inputs, we're finally ready to complete our Xylophone
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app.
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Given that we've just learned all about function parameters and function arguments, I'd like to start
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this lesson with the challenge.
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Can you modify the play sound function so that it can take a string input to an input of the data type
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string, and it's gonna be called Sound name, and then use that input instead of this hardcoded C letter,
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and finally, pass over this sender.CurrentTitle
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when you call the playSound function so that when you press any of the keys, it will play the corresponding
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sound?
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So pause the video and try to complete that challenge.
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All right.
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So first things first, let's add an input to this function play sound.
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Let's modify it. And we said that we were gonna call the input sound name, and then we were gonna give
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it the data type of a string.
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So now that we've modified our function, we can now use this soundName inside our function and we're
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gonna use it to replace this resource name.
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So instead of using just C every time we want to play a sound, we're gonna use that sound name that gets
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passed in,
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and that could be any one of the titles of our buttons.
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So now when I playSound, I'm going to pass over the soundName.
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Notice how it's telling me that I'm now missing an argument for the parameter soundName.
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And if I click on it, I can say Fix.
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So now it adds the parameter name which is what we specified here and it's expecting a value.
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Now, that value is not gonna be something I'm going to simply type out D or C, instead it's going to be
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based on what the sender.currentTitle is.
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So I'm going to cut it from there and paste it in here, and then I'm going to delete my print statement.
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Now, the final thing that we actually have to do is we have to click on this and simply click Fix on
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one of these options.
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Now, the one that I'm going to choose is an exclamation mark.
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And the reason why we need it and why we get that error is because the sender.currentTitle has
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a data type that is something that we would call an optional string,
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so the optional comes from the question mark.
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And it's because that we could have a button whose title is actually nil, it doesn't exist, in which case,
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we would be playing around with some nonexistent value and we'd be trying to pass it over to our
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playSound function, and then we would try to play a nonexistent value, and then our app will just come tumbling
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down.
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So the reason why this is an optional
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and it forces you to put in an exclamation mark is because it forces you to check and think, "Is there
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a situation where one of my buttons might not have a title?" And we can see that out of all of the buttons
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that's linked to our IBAction,
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they all have a title.
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So there's really no case where this can fail.
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So we can safely add an exclamation mark to say, don't worry, we've checked. It's always going to have
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a title,
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so we'll just send it over as the input to our playSound function.
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So now if I click on the C button, sender.currentTitle will be equal to C, and then C becomes the
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sound name, and C gets put in here,
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so then it plays C.wav, and it will change that depending on which button I press.
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So now let's run our app. And if I go ahead and click...
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Notice how every single key now has a different sound.
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And we've now completed our Xylophone app using a bit of knowledge about StackOverflow, about Google
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Search, as well as the Apple Documentation iOS Programming.
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So run your app and play the xylophone to your heart's content.
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And once you're done, we're going to tackle a boss challenge.