Stops all speech at the specified boundary constraint.
- iOS 7.0+
- macOS 10.14+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 3.0+
A constant describing whether speech should stop immediately or only after finishing the word currently being spoken.
YES if speech has stopped, or
Stopping the synthesizer cancels any further speech; in constrast with when the synthesizer is paused, speech cannot be resumed where it left off. Any utterances yet to be spoken are removed from the synthesizer’s queue.