问AVAudioRecorder块AVSpeechSynthesizer

EN

        self.synthesizer = [[AVSpeechSynthesizer alloc] init];
        self.synthesizer.delegate = self;
        NSString * toBeSpoken=[command.arguments objectAtIndex:0];
        NSNumber * rate=[command.arguments objectAtIndex:1];
        NSString * voice=[command.arguments objectAtIndex:2];
        NSNumber * volume=[command.arguments objectAtIndex:3];
        NSNumber * pitchMult=[command.arguments objectAtIndex:4];

        AVSpeechUtterance *utt =[[AVSpeechUtterance alloc] initWithString:toBeSpoken];

        utt.rate= [rate floatValue]/4;// this is to slow down the speech rate
        utt.volume=[volume floatValue];
        utt.pitchMultiplier=[pitchMult floatValue];
        utt.voice=[AVSpeechSynthesisVoice voiceWithLanguage:voice];

        [self.synthesizer speakUtterance:utt];

// returns whether or not audioSession is available - creates it if necessary
- (BOOL)hasAudioSession
{
    BOOL bSession = YES;

    if (!self.avSession) {
        NSError* error = nil;

        self.avSession = [AVAudioSession sharedInstance];
        if (error) {
                // is not fatal if can't get AVAudioSession , just log the error
            NSLog(@"error creating audio session: %@", [[error userInfo] description]);
            self.avSession = nil;
            bSession = NO;
        }
    }
    return bSession;
}

- (void)setAudioSession
{
    if ([self hasAudioSession]) {
        NSError* __autoreleasing err = nil;
        NSNumber* playAudioWhenScreenIsLocked = 0;
        BOOL bPlayAudioWhenScreenIsLocked = YES;
        if (playAudioWhenScreenIsLocked != nil) {
            bPlayAudioWhenScreenIsLocked = [playAudioWhenScreenIsLocked boolValue];
        }

        NSString* sessionCategory = bPlayAudioWhenScreenIsLocked ? AVAudioSessionCategoryPlayback : AVAudioSessionCategorySoloAmbient;
        [self.avSession setCategory:sessionCategory error:&err];
        if (![self.avSession setActive:YES error:&err]) {
                // other audio with higher priority that does not allow mixing could cause this to fail
            NSLog(@"Unable to play audio: %@", [err localizedFailureReason]);
        }
    }
}