Returns the mask of events monitored by the dispatch source.
- iOS 4.0+
- macOS 10.6+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
This parameter cannot be
The return value should be interpreted according to the type of the dispatch source, and can be one of the following flag sets:
The mask is a bitmask of relevant events being monitored by the dispatch event source. Any events that are not specified in the event mask are ignored and no event handler block is submitted for them.
For details, see the flag descriptions in Constants.