CAAnimationGroup timing - swift

Question

This is strange to me
For the following code (where myView is a coloured UIView on the storyboard) the timing seems off.
class ViewController: UIViewController {
#IBOutlet weak var myView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let round = CABasicAnimation(keyPath: "cornerRadius")
round.fromValue = 0.0
round.toValue = 50.0
round.duration = 2.0
round.beginTime = 0.0
round.fillMode = CAMediaTimingFillMode.backwards
round.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeIn)
myView.layer.cornerRadius = 50.0
let scaleDown = CABasicAnimation(keyPath: "transform.scale")
scaleDown.fromValue = 1.0
scaleDown.toValue = 0.25
scaleDown.beginTime = 2.0
scaleDown.duration = 2.0
let rotate = CABasicAnimation(keyPath: "transform.rotation")
rotate.fromValue = .pi/10.0
rotate.toValue = 0.0
rotate.beginTime = 4.0
rotate.duration = 2.0
let hideAnimation = CABasicAnimation(keyPath: "hidden")
hideAnimation.fromValue = NSNumber(value: 1)
hideAnimation.toValue = NSNumber(value: 0)
hideAnimation.beginTime = 4.0
hideAnimation.duration = 2.0
let imageGroupAnimations = CAAnimationGroup()
imageGroupAnimations.animations = [round, scaleDown, rotate, hideAnimation]
imageGroupAnimations.duration = 6.0
imageGroupAnimations.repeatCount = 1
imageGroupAnimations.beginTime = 0.0
myView.layer.add(imageGroupAnimations, forKey: nil)
}
}
The duration of the animation group is 6.0, so I would expect the shape to be hidden (since I expect it to be hidden from 4 to 4 + 2 (6.0) seconds.
However, the shape appears and finishes off the animation (finish rotating). I've tried using CACurrentMediaTime() in front of every beginTime - but this also doesn't have the expected result.
Expected result:
0-2 seconds animate corner radius change
2-4 seconds animate scale transformation
4-6 seconds animate rotation (hidden from the user)
How can I make the shape disappear from 4 - 6 seconds?

Answer 1

If you want to show fade-out effect on view, use
let hideAnimation = CABasicAnimation(keyPath: "opacity")
Instead of
let hideAnimation = CABasicAnimation(keyPath: "hidden") //bad!
If you don't want animation to reset your values after finish, simply add
imageGroupAnimations.fillMode = .forwards
imageGroupAnimations.isRemovedOnCompletion = false
to your CAAnimationGroup

Answer 2

The duration is not how long something stays true — it is how long it takes to perform a change.
So if you want the view to vanish suddenly, obviously you need to change hideAnimation.duration = 2.0 so that the duration is very short, say, 0.01.
This is a hideAnimation where the view turns invisible suddenly at the 4th second of the animation, and stays invisible until the end of the animation:
let hideAnimation = CABasicAnimation(keyPath: "hidden")
hideAnimation.fromValue = false
hideAnimation.toValue = true
hideAnimation.beginTime = 4.0
hideAnimation.duration = 0.01
hideAnimation.fillMode = .forwards
But I did not make any other changes because I still do not understand the complete effect that you want...