Defining Two Classes which Include the oppsite ones class causes a Redfinition Error

Question

I have two classes Object and Chassis and I include each class with the opposite ones header. This is causing a redefinition error. I understand why, but I don't know how to fix it. Here is the Code:

#ifndef GAME_h
#define GAME_h


#include "Object.h"

class Game{
     void AddObject(Object o);
     SDL_Renderer *GetRenderer(){ /*returns renderer*/ }
     /*random code*/
}

#endif

#ifndef OBJECT_h
#define OBJECT_h


#include "Game.h"

class Object{
     void CreateObject(/*settings*/);
     void SetTexture(Game g, const char* loc); //Uses Game to Load Texture
     /*random code*/
}

#endif

Thanks in advance!

When you ask about code you need to include the code ([mcve]) in the quesiton. — 463035818_is_not_an_ai, Apr 09 '20 at 17:47
from your example it is not apparent why you need the includes. Usually a forward declaration helps to resolve mutual includes — 463035818_is_not_an_ai, Apr 09 '20 at 17:53

score 0 · Accepted Answer · answered Apr 09 '20 at 17:59

0

You can declare a class first without a definition: The syntax would look like this: class Classname;

Make sure the declaration of this certain class will later be defined somewhere.

You can use the Classname class in the following part of the .h / .hpp file but you can not access its attributes and methods since they will be defined later.

Consider putting the method bodies, which need the attributes and methods of the other class, into a .cpp file.

For more details: https://en.cppreference.com/w/cpp/language/class

answered Apr 09 '20 at 17:59

nerotyc

16
3

By Method Bodies do you mean the functions inside of the classes like defining the function in the headers file and then adding actually code into the functions in a .cpp file? – Yami OG Apr 09 '20 at 18:02
exactly. You remove the part in parentheses from the .h file and put it into the .cpp file. – nerotyc Apr 09 '20 at 18:05
Should I make a header file to hold all the forward declarations? – Yami OG Apr 09 '20 at 18:17
As far as I can tell you already have two header files. If so, you don't need to make a new one. – nerotyc Apr 09 '20 at 18:28
Yeah thanks for the help it worked! – Yami OG Apr 09 '20 at 21:01

Defining Two Classes which Include the oppsite ones class causes a Redfinition Error

1 Answers1