Playing a "snap in/snap out" animation during zoom in, zoom out - ios

Question

So i got a set of rings one inside the other. I want to be able to zoom then in and, when I zoom close enough the zooming should animate the snap in and then I should keep zooming again.
I've done the zooming part pretty easily, using CGAffineTransform and UIPinchGesture recognizer, here is how the scale method looks like:
func scale(gesture: UIPinchGestureRecognizer) {
if !animationInProgress {
for var i = 0; i < scrollViews.count; i++ {
var view = scrollViews[i]
var j = 0
for ; j < scrollViews.count; j++ {
if view == scrollViews[j] {
break
}
}
println("Animation in progress: \(animationInProgress)")
if view.frame.origin.x < -80 || view.frame.origin.y < -140 {
if !view.hidden {
currentViewIndex = j + 1
view.hidden = true
view.visible = false
println("new view got out of the screen")
snapIn = true
animateSnap(snapIn)
}
} else {
if view.hidden == true {
currentViewIndex = j
view.hidden = false
view.visible = true
println("new view got into the screen")
snapIn = false
animateSnap(snapIn)
}
}
view.transform = CGAffineTransformScale(view.transform, gesture.scale, gesture.scale)
println("transformed")
}
gesture.scale = 1
}
}
so we iterate through our views, the frame.origin x and y checks, whether the views is out of the screen and I set some flags, which turn of some calculations.
The idea is the following, when one circle gets out of the screen, the rest animate zoom in and zoom out, when the new view gets on the screen.
Here is a animateSnap function:
private func animateSnap(snapIn: Bool) {
let factor: CGFloat = snapIn ? 1.5 : 0.5
for var a = currentViewIndex; a < scrollViews.count; a++ {
let next = scrollViews[a]
var transformAnimation = CABasicAnimation(keyPath: "transform")
transformAnimation.duration = 1
transformAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
transformAnimation.removedOnCompletion = false
transformAnimation.fillMode = kCAFillModeForwards
transformAnimation.delegate = self
let transform = CATransform3DScale(next.layer.transform, factor, factor, 1)
transformAnimation.toValue = NSValue(CATransform3D:transform)
next.layer.addAnimation(transformAnimation, forKey: "transform")
}
}
The question is: does somebody know an elegant solution to this or see any flaw in my approach ? The problem happens when the animation ends the views kinda go back to where they were at the start. I don't know why because remove on completion is set to false. In addition, can the fact that I use CGAffineTransform for zooming and CATransform3D somehow affect the result ?
Thank you very much !

Answer 1

For everybody who might encounter the same problem, when you work with 2D use CGAffineTransform instead of CATransform3D. That solved the problem, in addition I suspect that they also change different things(for example, CATransform3D changes layer) that's why when animation finished the result did not look as expected.