More keywords can be used as argument labels

Paul Hudson      @twostraws

Argument labels are a core feature of Swift, and let us write code like this:

for i in 1.stride(through: 9, by: 2) {
    print(i)
}

Without the through or by labels, this code would lose its self-documenting nature: what do the 9 and 2 do in 1.stride(9, 2)? In this example, Swift also uses the argument labels to distinguish 1.stride(through: 9, by: 2) from 1.stride(to: 9, by: 2), which produces different results.

As of Swift 2.2, you can now use a variety of language keywords as these argument labels. You might wonder why this would be a good thing, but consider this code:

func printGreeting(name: String, repeat repeatCount: Int) {
    for _ in 0 ..< repeatCount {
        print(name)
    }
}

printGreeting("Taylor", repeat: 5)

That uses repeat as an argument label, which makes sense because the function will print a string a number of times. Because repeat is a keyword, this code would not work before Swift 2.2 – you would need to write repeat instead, which is unpleasant.

Note that there are still some keywords that may not be used, specifically var, let and inout.

Other changes in Swift 2.2…

• ++ and -- are deprecated
• Traditional C-style for loops are deprecated
• Comparing tuples
• Tuple splat syntax is deprecated
• Variable parameters have been deprecated
• Renamed debug identifiers: line, function, file
• Stringified selectors are deprecated
• Compile-time Swift version checking

Download all Swift 2.2 changes as a playground Link to Swift 2.2 changes

Browse changes in all Swift versions