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Question

I am having an issue regarding closure escaping.The closure is defined as escaping but somehow the compiler always gives an error.

The error i get is

Closure use of non-escaping parameter 'completion' may allow it to escape .

I have also mentioned the places where i get the error.

Following is the code where closure is defined.

final internal class AnimationTemplate {

var  template: ((CompletionFunc) -> AnimationFunc)

init(template:  @escaping (CompletionFunc) -> AnimationFunc)
{
    self.template = template
}

func perform(with completion: CompletionFunc) { template(completion)() }
}

internal typealias CompletionFunc =  (( Bool) -> Void)

internal typealias AnimationFunc = (() -> Void)

Now it is used here.

AnimationQueue.shared.enqueue(animation: AnimationTemplate { completion in

  //Error here
  //Closure use of non-escaping parameter 'completion' may allow it to escape
  return {

     (0 ..< self.placeholderViews.count).forEach {

      let current: PasscodeSignPlaceholderView = self.placeholderViews[$0]

      let state: PasscodeSignPlaceholderView.State = $0 < inputLength ? .active : .inactive

      //Error here
      //Closure use of non-escaping parameter 'completion' may allow it to escape
      current.setState(to: state, with: completion)
    }
  }
})

I have seen a lot of other questions regarding this error issue but none seems to solve my problem.Any help will be highly appreciated.Thanks

Answer 1

Making the closure optional solved the issue.It was an eventual hit and trial.

 internal typealias CompletionFunc =  (( Bool) -> Void)?

I saw this closure was passed to a function which accepts an optional closure.Then I decided to make it optional.When i made it optional the error was gone. And xcode was giving me a wrong error perhaps.