C ++如何调用Objective-C方法？

Question

I'm using AudioQueue to analyze the audio frequency. I saw the SpeakHere example by Apple.

I know to use the callback function to get the audio data in inbuffer->mAudioData. The question is when I get the audio data, I want to update the spectrum on the UI. The UI is code use Objective-C and the SpeakHere code use C++. I don't know how to call the UI method in the callback function and pass the mAudioData.

Here is the callback function:

// AudioQueue callback function, called when an input buffers has been filled.

void AQRecorder::MyInputBufferHandler(  void *                              inUserData,     
                                    AudioQueueRef                       inAQ,
                                    AudioQueueBufferRef                 inBuffer,   
                                    const AudioTimeStamp *              inStartTime,
                                    UInt32                              inNumPackets,
                                    const AudioStreamPacketDescription* inPacketDesc)
{
   AQRecorder *aqr = (AQRecorder *)inUserData;
   aqr->currentQueueBufferRef = inBuffer;

   try {
       if (inNumPackets > 0) {
           // write packets to file
            XThrowIfError(AudioFileWritePackets(aqr->mRecordFile, FALSE, inBuffer->mAudioDataByteSize,
                                         inPacketDesc, aqr->mRecordPacket, &inNumPackets, inBuffer->mAudioData),
                   "AudioFileWritePackets failed");

        ***//Here I want to call Objective c Method and pass the value.***

    }

    // if we're not stopping, re-enqueue the buffe so that it gets filled again
    if (aqr->IsRunning())
        XThrowIfError(AudioQueueEnqueueBuffer(inAQ, inBuffer, 0, NULL), "AudioQueueEnqueueBuffer failed");
   } catch (CAXException e) {
    char buf[256];
    fprintf(stderr, "Error: %s (%s)\n", e.mOperation, e.FormatError(buf));
   }
}

Answer 1

If you want to use both C++ and Objective-C in the same file, please make sure the extension of the file is .mm instead of .m or .cpp . This way, the compiler knows it's Objective-C++ , and it compiles without a problem.

Somebody has explained it in detail in this blog post: Mixing Objective-C, C++ and Objective-C++