A context object that declares which parts of your layout need to be updated when the layout is invalidated.
- iOS 7.0+
- tvOS 9.0+
Layout objects that are designed to support invalidation contexts can use the information in a
UICollection object to optimize their behavior during the invalidation cycle. You can create an invalidation context object as a precursor to invalidating a layout object. After configuring the invalidation context object, pass it to the layout object’s
invalidate method, which is responsible for using the context object to update the layout efficiently. The collection view also creates invalidation contexts in response to specific changes. For example, it creates an invalidation context when you change the layout or data source object, when you insert or delete items, and when you call the
If you create your own custom layout objects, you can subclass
UICollection and add properties to specify which aspects of your layout data can be invalidated separately. You must then design your layout object to check for these properties and update the layout appropriately.
For more information about how to support custom invalidation contexts in your layout objects, see