Asks your data source object to provide the number of items in the specified section.
- macOS 10.11+
The collection view requesting the information.
The index number of the section. Section indexes are zero based.
The number of items in the specified section.
All data source objects must implement this method. Your implementation should quickly return the number of items in the specified section.
Make sure the number of items you return is accurate. The
collection method of your data source object must be able to provide a visual representation for each item in the section.