Question

I am having all sorts of problems with include-overload in my newbie C++ project, but I’m not sure how to avoid it.

How do I avoid the problem of having to include dozens of classes, for example in a map-loading scenario:

Here’s a trivial example Map class, which will load a game-map from a file:

// CMap.h
#ifndef _CMAP_H_
#define _CMAP_H_
class CMap {
    public:
        CMap();
        void OnLoad();
};
#endif

// CMap.cpp
#include "CMap.h"
CMap::CMap() {
}

void CMap::OnLoad() {
    // read a big file with all the map definitions in it here
}

Now let’s say I have a whole plethora of monsters to load into my map, so I might have a list or some other structure to hold all my monster definitions in the map

std::list<CMonster*> MonsterList;

Then I could simple forward-declare “CMonster” in my CMap.h, and add as many monsters as I like to that list

// CMap.h
class CMonster;

// CMap.cpp
void CMap::OnLoad() {
    // read a big file with all the map definitions in it here
    // ...
    // read in a bunch of mobs
    CMonster* monster;
    MonsterList.push_back(monster);
}

But what if I have lots of different types of monster? How do I create lots of different types of monster without including every CMonster_XXX.h? And also use methods on those?

// CMap.cpp
void CMap::OnLoad() {
    // read a big file with all the map definitions in it here
    // ...
    // read in a bunch of mobs
    CMonster_Kitten* kitty;
    kitty->OnLoad();
    MonsterList.push_back(kitty);

    CMonster_Puppy *puppy;
    puppy->OnLoad();
    puppy->SetPrey(kitty);
    MonsterList.push_back(puppy);

    CMonster_TRex *awesome;
    awesome->OnLoad();
    awesome->SetPrey(puppy);
    MonsterList.push_back(awesome);
}

Answer 1

Here’s the rule I use for including things.

• Forward declare as much as you can in your header files.
• include any .h you need in your .cpp
• don’t include .h in other .h unless you have to.
• If your project build without needing to include a .h, you are fine. (mostly, provided your compiler is compliant enough)

Edit: Additionally, you may want to read Large-Scale C++ Software Design. It talks about managing physical file dependencies.