UIViewController accepts non-escaping closure?

Using Swift
1

Just occurred to me today that UIKit methods like present() or dismiss() on view controllers now accept non-escaping closures. Is this a bug in documentation/SDK?

open func present(_ viewControllerToPresent: UIViewController, animated flag: Bool, completion: (() -> Void)? = nil)

open func dismiss(animated flag: Bool, completion: (() -> Void)? = nil)

See: dismiss(animated:completion:) | Apple Developer Documentation

2

Optional closures are always escaping.

3 Likes
3

Ah that's right! Thanks.

1 Like
4

Which is kind of a bug.... Could be worked around by either a longer:

open func present(_ vc: UIViewController, animated: Bool, completion: @escaping () -> Void) {
    ...
}
open func present(_ vc: UIViewController, animated: Bool) {
    present(vc, animated: animated) {}
}
open func dismiss(animated: Bool, completion: @escaping () -> Void) {
    ...
}
open func dismiss(animated: Bool, completion: @escaping () -> Void) {
    dismiss(animated: animated) {}
}

or a shorter:

open func present(_ vc: UIViewController, animated: Bool, completion: @escaping () -> Void = {}) {
    ...
}
open func dismiss(animated: Bool, completion: @escaping () -> Void = {}) {
    ...
}
5

Sure, but in this case they should be escaping.

6

Ah, yep, you are right. I meant situations when closures are turned from nonescaping to escaping by virtue of being optional.

7

Yes, your workarounds work when you want the closure to be nonescaping. Hopefully someday we will have nonescaping for all argument types.