How do I delay running a line of code until animations are finished? (DispatchGroup & DispatchQueue)

Question

I'm working in Swift 5 (Xcode 13.4.1) and I've got 3 animations that should run after a button is pressed. One of the animations, 'rotate', is defined by a function. The rotate animation doesn't stop after duration ends, it just restarts. I'm trying to stop the rotation animation using self.UI_Image_Name.layer.removeAllAnimations.

I can't get my code to wait until animations are finished to run the removeAllAnimations line. I've been trying to follow this tutorial: Waiting until the task finishes

Here's my current code:

@IBAction func flipButtonPress(_ sender: UIButton) {
        
//        flipResult.image = results[Int.random(in: 0...1)]
        
        
        self.animationGroup.enter()
        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now(), execute: { () -> Void in
        //Slide coin image to middle of screen
        UIView.animate(withDuration: 3, delay: 0,
                       options: [.curveEaseIn, .curveEaseOut],
                       animations: {
                            self.coinImage.frame.origin.y = 220
                       })
        //Rotate Coin image
            UIView.animate(withDuration: 11, delay: 3,
                           options: [.curveEaseIn, .curveEaseOut],
                           animations: {
                                self.coinImage.rotate()
            })
          //Fade away coin image
            UIView.animate(withDuration: 5, delay: 6,
                           options: [],
                           animations: {
                self.coinImage.alpha = 0.5
                                       
        })
            self.animationGroup.leave()
        })
        
        
        self.animationGroup.enter()
        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now(), execute: { () -> Void in
            self.coinImage.layer.removeAllAnimations()
        })
        self.animationGroup.leave()
        
    }
    
}

extension UIImageView{
    func rotate() {
        let rotation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
        rotation.toValue = NSNumber(value: (Double.pi * 2) * 22)
        rotation.duration = 11
        rotation.isCumulative = true
        rotation.repeatCount = Float.greatestFiniteMagnitude
        rotation.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeInEaseOut)
        rotation.beginTime = CACurrentMediaTime() + 3;
        self.layer.add(rotation, forKey: "rotationAnimation")
    }
}

Animations have nothing to do with Dispatch, so your plan is doomed to failure. There is a way to get a signal when the animation ends but that isn't it. — matt, Sep 02 '22 at 21:00
Perhaps you could make a suggestion for something to go learn about, rather than just say my plan is doomed to failure? Lolz — Joshua Johnson, Sep 03 '22 at 20:47
But you see, you did not ask how to detect the end of an animation. You asked how to do it _with Dispatch_. And my answer to _that_ is that you shouldn't and can't. That's called an xy question. — matt, Sep 03 '22 at 21:38

score -1 · Accepted Answer · answered Sep 02 '22 at 23:34

Simplist Option

Okay, so there's a lot of stuff here, for one, you can remove the animation group, as if its only purpose is to help run code when the animations are finished, then we won't need it.

Secondly, animations come with a completion callback. So change your Fade away coin image to this:

UIView.animate(withDuration: 5, delay: 6, options: []) {
    self.coinImage.alpha = 0.5
} completion: { _ in
    self.coinImage.layer.removeAllAnimations()
}

This means that after the 6 second delay and the 5 second animation, the coins layer animations will be removed

Another Option

If this doesn't create the desired effect, then instead you can try this (I personally try to avoid using this where I can as it can be prone to breaking if animation times are changed):

DispatchQueue.main.asyncAfter(deadline: .now() + <#Delay in seconds#>) {
     <#code#>
}

This will run the code inside the closure after the given number of seconds.

The first option did what I wanted. Thanks! – Joshua Johnson Sep 03 '22 at 20:56 — Joshua Johnson, Sep 03 '22 at 20:56

How do I delay running a line of code until animations are finished? (DispatchGroup & DispatchQueue)

1 Answers1

Simplist Option

Another Option