IOS7下，AVAudioRecorder需要注意的一点

      AVAudioSession * session =
      
         [AVAudioSession sharedInstance];

    NSError 
      
      * sessionError =
      
         nil;

    [session setCategory:AVAudioSessionCategoryPlayAndRecord error:
      
      &
      
        sessionError];

    
      
      
        if
      
       (session ==
      
         nil) {

        NSLog(
      
      
        @"
      
      
        Error creating session:%@
      
      
        "
      
      
        ,[sessionError description]);

    }

    
      
      
        else
      
      
         {

        [session setActive:YES error:nil];

    }