First of all, pardon my complete newbness as I'm completely new to developing on MAC along with Cocoa, and Obj-C So I'm doing some very basic trial and error testing, as I get accustomed to Objective C. Right now i have two simple classes. I have my model class which adds two numbers, and is written in C++. I also wrote a Controller class written in Objective C, which will handle functions when a Button is pressed on the GUI and will contain an instance of the model class. My question is, how can I succesfully compile this project, as the errors I'm getting lead me to believe I'm missing something in order to successfully mix the two languages. Thanks! P.S. I've tried renaming the ModelClass.cpp to ModelClass.mm and nothing happened.