How to identify CAAnimation within the animationDidStop delegate?

Question

I had a problem where I had a series of overlapping CATransition / CAAnimation sequences, all of which I needed to perform custom operations when the animations stopped, but

Answer 1

Xcode 9 Swift 4.0

You can use Key Values to relate an animation you added to the animation returned in animationDidStop delegate method.

Declare a dictionary to contain all active animations and related completions:

 var animationId: Int = 1
 var animating: [Int : () -> Void] = [:]

When you add your animation, set a key for it:

moveAndResizeAnimation.setValue(animationId, forKey: "CompletionId")
animating[animationId] = {
    print("completion of moveAndResize animation")
}
animationId += 1    

In animationDidStop, the magic happens:

    let animObject = anim as NSObject
    if let keyValue = animObject.value(forKey: "CompletionId") as? Int {
        if let completion = animating.removeValue(forKey: keyValue) {
            completion()
        }
    }