Swift4.2 Type 'UIBackgroundTaskIdentifier' (aka 'Int') has no member 'invalid'

Question

I'm getting a weird issue where code which works in one XCode project fails to compile in another. Both run Swift4.2.

Why do I get "UIBackgroundTaskIdentifier has no member 'invalid' error?

import UIKit import Foundation

//Type 'UIBackgroundTaskIdentifier' (aka 'Int') has no member 'invalid'
var backgroundTask: UIBackgroundTaskIdentifier = UIBackgroundTaskIdentifier.invalid

I can jump into the UIBackgroundTaskIdentifier definition and see this:

Answer 1

I had the same problem. Solved using UIBackgroundTaskInvalid instead of .invalid

var backgroundTask: UIBackgroundTaskIdentifier = UIBackgroundTaskInvalid

Not sure why it acts so strange. In the example from raywenderlich.com code compiles without errors.