title: Swift- animate CAshapeLayer stroke color
body: <p>I'm trying to find a way to animate the color of the stroke that I am creating      </p>
  
  <pre><code>circleLayer = CAShapeLayer()
  circleLayer.path = circlePath.CGPath
  circleLayer.lineCap =  kCALineCapRound
  circleLayer.fillColor = UIColor.clearColor().CGColor
  CABasicAnimation fill = CABasicAnimation.
  circleLayer.strokeColor = UIColor(red: 0.4, green: 1.0, blue: 0.2, alpha: 0.5).CGColor
  circleLayer.lineWidth = 20.0;
  circleLayer.lineJoin = kCALineJoinRound
  // Don't draw the circle initially
  circleLayer.strokeEnd = 0.0
  
  // Add the circleLayer to the view's layer's sublayers
  layer.addSublayer(circleLayer) 
  </code></pre>
  
  <p>What I want to achieve is: while it's being created (I'm creating it over a duration of 1 seconds), the color will animate itself.      </p>