Brilliant book which has helped immensely. One issue though is that the Animation stops if the App goes into Background. The sample code needs a way to restart the animation on return from Background.
I checked my version from a year ago, and yup, the animation did not run after returning from background. I did a Google, and found a pretty simple fix for that.
Add this line the didMoveToWindow() method in the AnimatedMaskLabel class, where you are setting up the animation:
gradientAnimation.isRemovedOnCompletion = false
That’s all it takes!