Shimmery is an app built around a UIView class, ShimmerView that allows you to add a Shimmer effect to any view heirarchy.
The Shimmer effect could be a way to emphasize a control item, or some task that is in progress.
To add Shimmer to any view, which would also add shimmer to all of that view's subviews, you merely add the ShimmerView to the mask:
_targetView.maskView = _shimmerView; // or _targetView.view.layer.mask = _shimmerView.layer;