The estimated size of cells in the collection view.
- iOS 8.0+
- tvOS 9.0+
Providing an estimated cell size can improve the performance of the collection view when the cells adjust their size dynamically. Specifying an estimate value lets the collection view defer some of the calculations needed to determine the actual size of its content. Specifically, cells that are not onscreen are assumed to be the estimated height.
The default value of this property is
CGSize. Setting it to any other value causes the collection view to query each cell for its actual size using the cell’s
preferred method. If all of your cells are the same height, use the
item property, instead of this property, to specify the cell size instead.