I tried to get AVSpeechSynthesizer audio file, but it gave me an error，Thread 1: Exception: “An AVSpeechUtterance shall not be enqueued twice”

Question

Here is my code: ...........

_avSpeaker = [[AVSpeechSynthesizer alloc] init];
speeechutterance = [[AVSpeechUtterance alloc] initWithString:textViewStr];
AVSpeechS