var engine:AVAudioEngine!
var format = engine.inputNode.inputFormat(forBus: 0)
engine.connect(engine.inputNode, to: engine.mainMixerNode, format: format)
in function AVAudioEngine.connect make my app crash only on hardware but in simulator it's fine.
When I run on hardware it's error says.
Terminating app due to uncaught exception 'com.apple.coreaudio.avfaudio', reason: 'required condition is false: IsFormatSampleRateAndChannelCountValid(format)'
terminating with uncaught exception of type NSException
I figure it out. I just set the AVAudioSession category type wrong. If you have the same error take a look at AVAudioSession and make sure that your AVAudioSession category is in the right setting for microphone permission. for instance
AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayAndRecord, with: .mixWithOthers)
with this setting will allow app to use microphone and play sound in the same time.