Support interactive animation with CALayer

Hi,

One of my views uses a CAShapeLayer to provide a line-dash. To date, I've been using the following technique to capture if there is an animation in progress in the layer's containing view and apply it to the layer also:

Code Block 
override func layoutSubviews() {
    let layerBoundsSizeAnimation = layer.animation(forKey: "bounds.size")
    CATransaction.begin()
    if let layerBoundsSizeAnimation = layerBoundsSizeAnimation {
        CATransaction.setAnimationDuration(
            layerBoundsSizeAnimation.duration)
        CATransaction.setAnimationTimingFunction(
            layerBoundsSizeAnimation.timingFunction)
        let pathAnimation = CABasicAnimation(keyPath: "path")
        borderLayer.add(pathAnimation, forKey: "path")
    } else {
        CATransaction.setDisableActions(true)
    }
    borderLayer.path = CGPath(rect: bounds, transform: nil)
    CATransaction.commit()
}

This works well for non-interactive animations.

However, when I try to perform an interactive animation (i.e pausing a UIViewPropertyAnimator and adjusting its fractionComplete property) the layer animation fails to pause and simply continues to its end position.

Is there a simple way to setup a view's layer hierarchy to support the interactive animation of its sublayers?