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How to unwrap an optional in Swift

Paul Hudson       @twostraws

Optional values are a central concept in Swift, although admittedly they can be a little hard to understand at first. Put simply, an optional value is one that may or may not exist, which means Swift won't let you use it by accident – you need to either check whether it has a value and unwrap it, or force unwrap. Of the two options the first is definitely preferable, because it's significantly safer.

To check whether an optional has a value then unwrap it all in one, you should use if let syntax, like this:

// fetch an example optional string
let optionalString = fetchOptionalString()

// now unwrap it
if let unwrapped = optionalString {
    print(unwrapped)
}

In that example, the print(unwrapped) line will only be executed if optionalString has a value. If that line is reached, you can know for sure that unwrapped has a value that you can use, which makes that code safe.

Available from iOS 7.0 – see Hacking with Swift tutorial 1

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