addBoundaryTimeObserver(forTimes:queue:using:)
Requests invocation of a block when specified times are traversed during normal rendering.
Declaration
func addBoundaryTimeObserver(forTimes times: [NSValue], queue: dispatch_queue_t?, using block: @escaping @Sendable () -> Void) -> AnyParameters
- times:
An array containing the times for which the observer requests notification.
- queue:
The serial queue the block should be unqueued on. If you pass
NULL, the main queue is used. Passing a concurrent queue results in undefined behavior. - block:
The block to be invoked when any of the specified times is crossed during normal rendering.
Return Value
An object that conforms to NSObject. You must retain this value as long as you want the time observer to be invoked by the synchronizer. Pass this object to removeTimeObserver(_:) to cancel time observation.
Discussion
Always pair a call to this method with a call to removeTimeObserver(_:). Releasing the observer without calling removeTimeObserver(_:) results in undefined behavior.