NEW: Learn to build the incredible iOS 15 Weather app today! >>

Renamed debug identifiers: line, function, file

Available from Swift 2.2

Paul Hudson      @twostraws

Swift 2.1 and earlier used the "screaming snake case" symbols __FILE__, __LINE__, __COLUMN__, and __FUNCTION__, which automatically get replaced the compiler by the filename, line number, column number and function name where they appear.

From Swift 2.2, those old symbols have been replaced with #file, #line, #column and #function, which will be familiar to you if you've already used Swift 2.0's #available to check for iOS features. As the official Swift review says, it also introduced "a convention where # means invoke compiler substitution logic here."

Here’s how the debug identifiers in action from Swift 2.2 and later:

func printGreeting(name: String, repeat repeatCount: Int) {
    print("This is on line \(#line) of \(#function)")

    let upperName = name.uppercaseString

    for _ in 0 ..< repeatCount {
        print(upperName)
    }
}

printGreeting("Taylor", repeat: 5)
Hacking with Swift is sponsored by Essential Developer

SPONSORED Learn the most up-to-date techniques and strategies for testing new and legacy Swift code in this free practical course for iOS devs who want to become complete Senior iOS Developers.

Learn more

Sponsor Hacking with Swift and reach the world's largest Swift community!

Other changes in Swift 2.2…

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

Browse changes in all Swift versions

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.