UICollection protocol defines methods that let you coordinate with a
UICollection object to implement a grid-based layout. The methods of this protocol define the size of items and the spacing between items in the grid.
- iOS 6.0+
- tvOS 9.0+
All of the methods in this protocol are optional. If you do not implement a particular method, the flow layout delegate uses values in its own properties for the appropriate spacing information.
The flow layout object expects the collection view’s delegate object to adopt this protocol. Therefore, implement this protocol on object assigned to your collection view’s