如何在iOS中以编程方式切换到earSpeaker？

AVAudioSession *audioSession = [AVAudioSession sharedInstance];
NSError *error = nil;
[audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&error];
if (error) {
    NSLog(@"设置音频会话错误：%@", error.localizedDescription);
    return;
}
[audioSession overrideOutputAudioPort:AVAudioSessionPortOverrideSpeaker error:&error];
if (error) {
    NSLog(@"切换到earSpeaker错误：%@", error.localizedDescription);
    return;
}

NSError *error = nil;
[[AVAudioSession sharedInstance] overrideOutputAudioPort:AVAudioSessionPortOverrideNone error:&error];
if (error) {
    NSLog(@"切换到默认音频输出错误：%@", error.localizedDescription);
    return;
}