Thread: is not a class or namespace name (But i'm sure it is)

GameState.h includes GameStateManager.h and vice versa. You'll need to break the circular dependency by not including the other in one header.

It appears that the declaration of CGameState doesn't need to know anything about CGameStateManager. You'll need to move the implementation of at least those methods that use CGameStateManager to a separate source file.

#include means: take this file and paste it at the place of the macro (because of the header guards - if it hasn't been included in this compilartion unit already).

So, OgreTest.cpp includes GameStateManager.h. GameStateManager.h includes GameState.h. GameState.h has #include "GameStateManager.h", but that header has already been included for OgreTest.cpp.

So, for OgreTest.cpp the compilation unit that the compiler will work with contains:

Code:

class CGameState
{
    //...
    //using CGameStateManager
};

class CGameStateManager
{
     //...
};

int main()
{
    //...
}

As you can see, CGameState ends up using CGameStateManager which will be declared later on. In C++ you can use only things that have been declared / defined earlier.

The solution is not to rearrange includes carefully. The solution is to separate declarations and implementations, and use forward declarations in more complicated cases (not the case here).