How to access objective c defined classes from c++ game.

I know this is done with SimpleAudioEngine.

It’s just that SimpleAudioEngine has a lot going on and it’s hard to figure out how to do it by just analyzing it’s files.

Can someone put a simple example on how to access objective-c classes from the game in c++?

I need to know how to do this so that I can implement In-app purchases and Admob.

I would really appreciate help with this.