Masking of iOS core animations

1. Application Scenarios
   You want to make some scrolls of text slowly fade into the background color, rather than an abrupt boundary layer border is not rounded, but a picture of a star frame
2. Method
   Sets the Mask property. This property is also a layer property, but only the Alpha property has an effect. That is, the product of the Alpha property of the image and the alpha attribute of the Masklayer is the final alpha.
3. Advantages
   ???? The real calayer of the mask layer is that the mask diagram is not limited to static plots. Any layer that has layers can be used as the Mask property, which means that your mask can be generated in real time through code or even animations.

Masking of iOS core animations