An individual dimension of an item's size (width or height) in a collection view.
- iOS 13.0+
- macOS 10.15+
- Mac Catalyst 13.0+
- tvOS 13.0+
Each item in a collection view has an explicit width dimension and height dimension, which combine to define the item's size (
You can express an item's dimensions using an absolute, estimated, or fractional value.
Use an absolute value to specify exact dimensions, like a 44 x 44 point square:
Use an estimated value if the size of your content might change at runtime, such as when data is loaded or in response to a change in system font size. You provide an initial estimated size and the system computes the actual value later.
Use a fractional value to define a value that's relative to a dimension of the item's container. This option simplifies specifying aspect ratios. For example, the following item has a width and a height that are both equal to 20% of its container's width, creating a square that grows and shrinks as the size of its container changes.