Functional Programming: A PragPub Anthology

Fancy Return Types

In Swift, function return types and values can get a bit more complex than we’re used to in Objective-C, especially with the introduction of optionals and multiple return types.

Optional Return Types

If there is a possibility that your function could return a nil value, you need to specify the return type as optional:

func myFuncWithOptionalReturnType() -> String? {
    let someNumber = arc4random() % 100
    if someNumber > 50 {
        return "someString"
    } else {
        return nil
    }
}

myFuncWithOptionalReturnType()

And of course, when you’re using the optional return value, don’t forget to unwrap:

let optionalString = myFuncWithOptionalReturnType()

if let someString = optionalString {
 println("The function returned ...