Returns whatever type on the pasteboard would be most preferred for copying data.
- macOS 10.0+
The types currently available on the pasteboard.
Types allowed in the return value. If
nil, any available type is allowed.
The preferred type to provide given the available types and the allowed types.
You should not need to override this method. You should also not need to invoke it unless you are implementing a new type of pasteboard to handle services other than copy/paste or dragging.