This simple project show some aspects of collection view layout implementation.

App contains 3 examples:

1. Example of subclassed UICollectionViewFlowLayout implementing footer view as decoration view with custom layout attributes.
2. Example of subclassed UICollectionViewLayout implementing separators view as decoration view and custom layout animations.
3. Example of subclassed UICollectionViewLayout where cells use auto-layout to calculate cell size. This example show how use UICollectionViewLayoutInvalidationContext to achieve better performance.