Proper way to combine objective-c and c++?
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I'm working on an app that will do some real time processing of input audio.  I found [this](http://teragonaudio.com/article/How-to-do-realtime-recording-with-effect-processing-on-iOS.html) site that I think I can use as a starting point.  However, all the functions provided are in C++.

The simplest thing I'd like to get going first is changing the text of a UILabel to some of the values received by the function: 

    OSStatus renderCallback(void *userData, AudioUnitRenderActionFlags *actionFlags,
                        const AudioTimeStamp *audioTimeStamp, UInt32 busNumber,
                        UInt32 numFrames, AudioBufferList *buffers)

I pasted all the functions into the @implementation of my view and was able to compile by changing the extension to .mm.  I created a UILabel property, but the renderCallback function can't access it.  

Obviously just pasting those functions into the @implementation isn't the right way to be doing this.  How do I do it the right way?