gistfile1.txt

    NSArray *pathComponents = @[[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject],
                                fileName];
    NSURL *outputFileURL = [NSURL fileURLWithPathComponents:pathComponents];
    AudioFileWriter *fileWriter = [[AudioFileWriter alloc]
                                   initWithAudioFileURL:outputFileURL
                                   samplingRate:_audioManager.samplingRate
                                   numChannels:_audioManager.numInputChannels];

    float data[_loopLength * _audioManager.numInputChannels];
    _loopBuffer->FetchInterleavedData(data, _loopLength, _audioManager.numInputChannels);
    [fileWriter writeNewAudio:data
                    numFrames:_loopLength
                  numChannels:_audioManager.numInputChannels];