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Checkpoint 9

Paul Hudson    @twostraws   

Updated for Xcode 13.2

Now that you understand a little about optionals, it’s time to pause for a few minutes and try a small coding challenge so you can see how much you’ve remembered.

Your challenge is this: write a function that accepts an optional array of integers, and returns one randomly. If the array is missing or empty, return a random number in the range 1 through 100.

If that sounds easy, it’s because I haven’t explained the catch yet: I want you to write your function in a single line of code. No, that doesn’t mean you should just write lots of code then remove all the line breaks – you should be able to write this whole thing in one line of code.

I’ll provide some hints in a moment, but first I recommend you go ahead and try it yourself.

Hacking with Swift+ subscribers can get a complete video solution for this checkpoint here: Solution to Checkpoint 9. If you don’t already subscribe, you can start a free trial today.

Still here? Okay, here are some hints:

  1. Your function should accept an [Int]? – an array of integers that might be there, or might be nil.
  2. It needs to return a non-optional Int.
  3. You can use optional chaining to call randomElement() on the optional array, which will in turn return another optional.
  4. Because you need to return a non-optional integer, you should use nil coalescing to pick a random number from 1 through 100.
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