Adds a CFRunLoopObserver object to a run loop mode.
- iOS 2.0+
- macOS 10.0+
- tvOS 9.0+
- watchOS 2.0+
- Core Foundation
The run loop to modify.
The run loop observer to add.
The run loop mode to which to add
observer. Use the constant
observerto the set of objects monitored by all the common modes.
A run loop observer can be registered in only one run loop at a time, although it can be added to multiple run loop modes within that run loop.
rl already contains
mode, this function does nothing.