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Summary: Conditions and loops

Paul Hudson    @twostraws   

We’ve covered a lot about conditions and loops in the previous chapters, so let’s recap:

  • We use if statements to check a condition is true. You can pass in any condition you want, but ultimately it must boil down to a Boolean.
  • If you want, you can add an else block, and/or multiple else if blocks to check other conditions. Swift executes these in order.
  • You can combine conditions using ||, which means that the whole condition is true if either subcondition is true, or &&, which means the whole condition is true if both sub conditions are true.
  • If you’re repeating the same kinds of check a lot, you can use a switch statement instead. These must always be exhaustive, which might mean adding a default case.
  • If one of your switch cases uses fallthrough, it means Swift will execute the following case afterwards. This is not used commonly.
  • The ternary conditional operator lets us check WTF: What, True, False. Although it’s a little hard to read at first, you’ll see this used a lot in SwiftUI.
  • for loops let us loop over arrays, sets, dictionaries, and ranges. You can assign items to a loop variable and use it inside the loop, or you can use underscore, _, to ignore the loop variable.
  • while loops let us craft custom loops that will continue running until a condition becomes false.
  • We can skip some or all loop items using continue or break respectively.

That’s another huge chunk of new material, but with conditions and loops you now know enough to build some really useful software – give it a try!

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