Question

I have a class defined in class.cpp and class.h. The class uses some structures/classes/types/whatever defined in stuff.h (and of course, stuff.cpp) for private members and methods. My main program is in main.cpp, which #includes class.h, but doesn’t care about anything in stuff.h. If it makes a difference, class.cp is supposed to be loaded dynamically (.dll/.so).
I would ideally like to have the stuff.h only included in class.cpp and stuff.cpp linked only to this file, as they would just cause name-space pollution in main.cpp and extra bloat by being linked to the final program.
The problem is that I have to include stuff.h in class.h, since it’s definitions are used in the private: part of my class, which is all in class.h. And since main.cpp brings in class.h, it also gets stuff.h!

I hope this was clear. In C# this can be solved by partial classes. How would I do this in C++?

Answer 1

You do that in C++ by using pImpl aka Opaque Pointers where the class you expose only have one attribute which is a partially defined struct (sometimes people uses void* instead, but to same efefct).

The partially defined struct, then is fully defined inside your stuff.cpp and everything works as you expect — the only snag is that you need to make sure that you constructor and destructor new/delete the internal implementation, and you need to make special provisions in your copy constructor and and your assignment operator operator= — most people opt for just make the copy constrctor and assignment operators private, so that the compiler will object if they are used.