CoreAnimation and CAReplicatorLayer in Swift?

Question

I'm porting this library from objc to Swift and I'm having problems finding out why the replicator layer instanceCount is not doing anything to the animation. Any thoughts?

If you look at the library it has multiple instances of the layer animating at the same time, but in my code, only a single layer animates at a time.

https://github.com/shu223/PulsingHalo/blob/master/PulsingHalo/PulsingHaloLayer.m

public class PulsingHaloLayer2: CAReplicatorLayer {

    var fromValueForRadius: Float = 0.0
    var fromValueForAlpha: Float = 0.45
    var keyTimeForHalfOpacity: Float = 0.2
    var animationDuration: NSTimeInterval = 3.0
    var pulseInterval: NSTimeInterval = 0.0
    var useTimingFunction: Bool = true
    let animationGroup: CAAnimationGroup = CAAnimationGroup()
    var repetitions: Float = Float.infinity
    var radius: CGFloat = 200.0 {
        didSet {
            let tempPos = position
            let diameter = radius * 2

            bounds = CGRect(x: 0.0, y: 0.0, width: diameter, height: diameter)
            cornerRadius = radius
            position = tempPos
        }
    }
    var haloLayerNumber: Int = 4 {
        didSet {
            instanceCount = 4
            instanceDelay = (animationDuration + pulseInterval) / Double(haloLayerNumber)
        }
    }

    override init() {
        super.init()
        contentsScale = UIScreen.mainScreen().scale
        opacity = 0.0
        backgroundColor = UIColor.blueColor().CGColor
        haloLayerNumber = 4

        setupAnimationGroup()
        addAnimation(animationGroup, forKey: "pulse")
    }

    required public init(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func setupAnimationGroup() {
        animationGroup.duration = animationDuration + pulseInterval
        animationGroup.repeatCount = repetitions
        animationGroup.removedOnCompletion = false

        if useTimingFunction {
            let defaultCurve = CAMediaTimingFunction(name: kCAMediaTimingFunctionDefault)
            animationGroup.timingFunction = defaultCurve
        }

        let opacityAnimation = CAKeyframeAnimation(keyPath: "opacity")
        opacityAnimation.duration = animationDuration
        opacityAnimation.values = [fromValueForAlpha, 0.45, 0]
        opacityAnimation.keyTimes = [0, keyTimeForHalfOpacity, 1]

        let scaleAnimation = CABasicAnimation(keyPath: "transform.scale.xy")
        scaleAnimation.fromValue = fromValueForRadius
        scaleAnimation.toValue = 1
        scaleAnimation.duration = animationDuration

        animationGroup.animations = [opacityAnimation, scaleAnimation]
    }

}

Answer 1

When you call haloLayerNumber = 4, this does not trigger the didSet block, because it's happening inside of init.

You can work around this using a closure: ({ haloLayerNumber = 4 })(). Or you can manually update the instanceCount/instanceDelay from inside of init.