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.

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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