How can I chain Core Animations for different Layers one after the other?

Question

I have a scrollView with paging enabled and a number N of pages, which are UIViews as subviews of the scrollView.

I\'m trying to do the following:

User scrolls t

Answer 1

In Swift 3 (layers is an array of CALayer or CAShapeLayer)

var timeOffset:Double = 0
for layer in layers {
    let a = CABasicAnimation(keyPath: "path"
    a.fromValue = layer.ovalPathSmall.cgPath
    a.toValue = layer.ovalPathLarge.cgPath
    a.fillMode = kCAFillModeForwards
    a.beginTime = CACurrentMediaTime() + timeOffset
    a.duration = 0.3
    a.isRemovedOnCompletion = false
    layer.add(a, forKey: nil)

    timeOffset += 0.3
}

And in case you're wondering what ovalPathSmall and ovalPathLarge are:

ovalPathSmall = UIBezierPath(arcCenter: position, radius: smallRadius, startAngle: 0, endAngle: 2 * .pi, clockwise: true)
ovalPathLarge = UIBezierPath(arcCenter: position, radius: largeRadius, startAngle: 0, endAngle: 2 * .pi, clockwise: true)