Wait for Swift animation to complete before executing code

Question

I am trying to animate a UIImageView and then hide the image view after animation is complete. However the imageview gets hidden before the animation is completed. I looked

Answer 1

As Paulw11 alluded to in his comment, you can use the animationDidStop: method mentioned in the docs. But furthermore, you should add a key to you CABasicAnimation/CAAnimation objects such that your animationDidStop: method knows which one in particular has completed.

So in your shake method add a value-key pair to identify the animation and set the delegate to self, ex:

func shakeView(iv: UIImageView){

    var shake:CABasicAnimation = CABasicAnimation(keyPath: "position")
    shake.duration = 0.1
    shake.repeatCount = 2
    shake.autoreverses = true

    // Add these two lines:
    shake.setValue("shake", forKey: "animationID")
    shake.delegate = self

    // ...

Then add the animationDidStop: delegate method to alert you as to when the animation is complete so you can start executing your code:

override func animationDidStop(anim: CAAnimation!, finished flag: Bool) {
    // Unwrap the optional value for the key "animationID" then
    // if it's equal to the same value as the relevant animation,
    // execute the relevant code
    if let animationID: AnyObject = anim.valueForKey("animationID") {
        if animationID as NSString == "shake" {
            // execute code
        }
    }
}

Answer 2

You can use a CATransaction to call a completion block after the animation completes.

func shakeView(iv: UIImageView){

    CATransaction.begin()
    CATransaction.setCompletionBlock({
        iv.hidden = true
    })
    var shake:CABasicAnimation = CABasicAnimation(keyPath: "position")
    shake.duration = 0.1
    shake.repeatCount = 21
    shake.autoreverses = true

    var from_point:CGPoint = CGPointMake(iv.center.x - 5, iv.center.y)
    var from_value:NSValue = NSValue(CGPoint: from_point)

    var to_point:CGPoint = CGPointMake(iv.center.x + 5, iv.center.y)
    var to_value:NSValue = NSValue(CGPoint: to_point)

    shake.fromValue = from_value
    shake.toValue = to_value
    iv.layer.addAnimation(shake, forKey: "position")
    CATransaction.commit()
}

Or you can also group both animations together in a CATransaction as follows.

func shakeView(iv: UIImageView){
    var shake:CABasicAnimation = CABasicAnimation(keyPath: "position")
    shake.duration = 0.1
    shake.repeatCount = 21
    shake.autoreverses = true

    var from_point:CGPoint = CGPointMake(iv.center.x - 5, iv.center.y)
    var from_value:NSValue = NSValue(CGPoint: from_point)

    var to_point:CGPoint = CGPointMake(iv.center.x + 5, iv.center.y)
    var to_value:NSValue = NSValue(CGPoint: to_point)

    shake.fromValue = from_value
    shake.toValue = to_value
    iv.layer.addAnimation(shake, forKey: "position")
}

override func viewDidLoad() {
    CATransaction.begin()

    CATransaction.setCompletionBlock({
        self.image1.hidden = true
        self.image2.hidden = true
    })
    shakeView(image1)
    shakeView(image)
  CATransaction.commit()
}