# CFRunLoopIsWaiting(_:) Returns a Boolean value that indicates whether the run loop is waiting for an event. ``` func CFRunLoopIsWaiting(_ rl: CFRunLoop!) -> Bool ``` ## Parameters `rl` The run loop to examine. ## Return Value `true` if `rl` has no events to process and is blocking, waiting for a source or timer to become ready to fire; `false` if `rl` either is not running or is currently processing a source, timer, or observer. ## Discussion This function is useful only to test the state of another thread’s run loop. When called with the current thread’s run loop, this function always returns `false`. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)