Returns the supplementary view associated with the specified index path.
- macOS 10.11+
The kind of the supplementary views you want returned. The layout object defines the kinds of supplementary views it supports. This parameter must not be
The index path whose supplementary view you want.
The view for the specified index path or
nil if no view is available.
For efficiency, the collection view does not create supplementary views until they are needed. Typically, views are created only when they need to be displayed onscreen. If the collection view does not currently have a supplementary view for the specified index path, because that view would be positioned offscreen, this method returns