The Core iOS Developer’s Cookbook, Fifth Edition

Data Sources and Delegates

View controllers coordinating collection views declare UICollectionViewDataSource and UICollectionViewDelegate. Unlike with table views, when using a flow layout, a third protocol is also declared, UICollectionViewDelegateFlowLayout.

The delegate flow layout protocol coordinates layout information with your collection’s layout instance through a series of callbacks. Your collection view’s delegate adopts this protocol—that is, you do not have to specify a third collection view property like delegateFlowLayout.

As with table views, the data source provides section and item information and returns cells and other collection view items on demand. The delegate handles user interactions and provides meaningful responses ...