CHHapticEngine: Properly stop engine after a playback - ios

Question

I was trying to play a haptic "AHAP" pattern from a file with the following code:
__strong static CHHapticEngine *engine;
engine = [[CHHapticEngine alloc] initAndReturnError:nil];
[engine startAndReturnError:nil];
[engine playPatternFromURL:[NSURL fileURLWithPath:#"/path/to/pattern.ahap"] error:nil];
The haptics does play successfully, but I have an issue that whenever was pattern is played, the first key press on keyboard make very loud flick sound (the default iOS flick sound) and subsequently back to normal on second press. I thought it was because the engine is still active, so I called
[engine stopWithCompletionHandler:nil];
but then the haptic doesn't play anymore (however, flick sound is normal for first key press). playPatternFromURL:error: is supposed to play synchronously, which means it'll finish playing before executing stopWithCompletionHandler: (from Apple Doc). I honestly has no idea why and how this happens. CoreHaptics rarely can be seen implemented in the wild and github except the official Apple Doc, so I have no useful references (maybe except this in github).
Any idea on this particular issue? Thanks in advance.
EDIT:
For future reader, I managed to mitigate this issue by playing it in another thread:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[engine playPatternFromURL:[NSURL fileURLWithPath:#"/path/to/pattern.ahap"] error:nil];
});
Perhaps this is due to the Frameworks being a beta software as of writing.
EDIT 2:
Above mitigation however doesn't solve it if you have CHHapticEventTypeAudioCustom

Answer 1

I managed to solve it using these codes below:
__strong static CHHapticEngine *engine;
engine = [[CHHapticEngine alloc] initAndReturnError:nil];
[engine startAndReturnError:nil];
[engine playPatternFromURL:[NSURL fileURLWithPath:#"/path/to/pattern.ahap"] error:nil];
[engine notifyWhenPlayersFinished:^CHHapticEngineFinishedAction(NSError * _Nullable error) {
[engine stopWithCompletionHandler:nil];
return CHHapticEngineFinishedActionStopEngine;
}];
It seems like I needs to observe whenever the pattern stopped playing and stop the engine (not due to the framework being a beta software, my bad). However, for the method playPatternFromURL:error:, quoting from Apple Doc:
This method blocks processing on the current thread until the pattern
has finished playing.
doesn't seems to means what it means, at least to my understanding. That's why calling stopWithCompletionHandler: right after playPatternFromURL:error: failed to trigger any haptics.

Answer 2

Solution:
engine.playsHapticsOnly = YES;