Returns the run loop stages during which an observer runs.
- iOS 2.0+
- macOS 10.0+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
The run loop observer to examine.
A bitwise-OR combination of all the run loop stages in which
observer is called. See
CFRunLoopActivity for the list of stages.
CFRunLoopObserver Miscellaneous Functions
Returns a Boolean value that indicates whether a CFRunLoopObserver object is valid and able to fire.
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