Returns a Boolean value that indicates whether a CFRunLoopObserver repeats.
- iOS 2.0+
- macOS 10.0+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
- Core Foundation
The run loop observer to examine.
observer is processed during every pass through the run loop;
observer is processed once and then is invalidated.