我目前有一个Swift应用程序，它可以将一个正方形的填充颜色从红色更改为绿色。我希望发生的是，当动画完成后，我会执行更多的代码。
这是我的档案：

import UIKit

class PathViewController: TapToCloseViewController {

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)

        let tempView = UIView(frame: CGRectMake(0,0,100,100))
        tempView.layer.borderColor = UIColor.blackColor().CGColor
        tempView.layer.borderWidth = 2
        view.addSubview(tempView)

        let bounds = CGRect(x: 0, y: 0, width: 100, height: 100)

        // Create CAShapeLayerS
        let rectShape = CAShapeLayer()
        rectShape.bounds = bounds
        rectShape.position = tempView.center
        rectShape.cornerRadius = bounds.width / 2
        tempView.layer.addSublayer(rectShape)
        tempView.backgroundColor = UIColor.redColor()

        // Apply effects here

        // fill with white
        rectShape.fillColor = UIColor.greenColor().CGColor

        // 1
        // begin with a circle with a 50 points radius
        //let startShape = UIBezierPath(roundedRect: bounds, cornerRadius: 50).CGPath
        let sRect = CGRect(x:0, y:0, width: 0, height: bounds.height)
        let bpath = UIBezierPath(rect: sRect).CGPath

        // animation end with a large circle with 500 points radius
        let drect = CGRect(x:0, y:0, width: bounds.width, height: bounds.height)
        let endShape = UIBezierPath(rect: drect).CGPath

        //let endShape = UIBezierPath(roundedRect: CGRect(x: -450, y: -450, width: 1000, height: 1000), cornerRadius: 500).CGPath

        // set initial shape
        rectShape.path = bpath

        // 2
        // animate the `path`
        let animation = CABasicAnimation(keyPath: "path")
        animation.toValue = endShape
        animation.duration = 1 // duration is 1 sec
        // 3
        animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut) // animation curve is Ease Out 
        animation.fillMode = kCAFillModeBoth // keep to value after finishing
        animation.removedOnCompletion = false // don't remove after finishing
        // 4 
        rectShape.addAnimation(animation, forKey: animation.keyPath)

    }

}

如何检测动画何时停止？