Calling a Objective C function from C++ Code

Question

I googled around and I find a million results to this subject. But none of the pages helps me. I think that I have a very common problem. I\'m playing around with audio programm

Answer 1

self only exists in Objective-C methods and that is a C style function. You need to pass self from an Objective-C method to the inUserData when you set up the callback, then cast it back to the correct type.

//This is an example for using AudioQueueNewInput
//Call this in an Objective-C method passing self to inUserData
AudioQueueNewInput (
   const AudioStreamBasicDescription  *inFormat,
   AudioQueueInputCallback            inCallbackProc,

   // this is where you will pass (void*)self
   void                               *inUserData, 
   CFRunLoopRef                       inCallbackRunLoop,
   CFStringRef                        inCallbackRunLoopMode,
   UInt32                             inFlags,
   AudioQueueRef                      *outAQ
);

And your original implementation

static void HandleInputBuffer (void                                 *aqData,
                           AudioQueueRef                        inAQ,
                           AudioQueueBufferRef                  inBuffer,
                           const AudioTimeStamp                 *inStartTime,
                           UInt32                               inNumPackets,
                           const AudioStreamPacketDescription   *inPacketDesc ) 
{
    AudioRecorder *ar_instance = (AudioRecorder*)aqData;
    ...
    [ar_instance playAlarmSound];
    ...
}