//[Player .h]
...
...
#include "cball.h"
...
...
//[Ball.h]
...
...
#include "cPlayer.h"
...
...
3's a crowd!
Author
Hi guys,
I have a base class object, and 2 classes ball and player which inherit from this class.
Now i need my player class to have a pointer to the ball in order to influence it by calling its object class functions(physics). However i would also like my ball to see the player class? But i cannot set this up in the #includes as they call each other before either has been declared!? Understand?
Example..
Player class
Author
Err I know is pointers!Thats a given!
But the #includes are the problem, when making my player class its told to include the ball class so i can have a pointer to a ball, so it reads the ball class. However the ball class has #include "player.h" as it needs the player class(As it has a pointer to a player!).
So it gets stuck
But the #includes are the problem, when making my player class its told to include the ball class so i can have a pointer to a ball, so it reads the ball class. However the ball class has #include "player.h" as it needs the player class(As it has a pointer to a player!).
So it gets stuck
forward declaration, search for it on google.
Basicly,
declare an empty class cPlayer in cball.h
and an empty class cBall in cplayer.h
then include cball.h and cplayer.h in cpp files.
Basicly,
declare an empty class cPlayer in cball.h
and an empty class cBall in cplayer.h
then include cball.h and cplayer.h in cpp files.
you need to do forward declarations of the classes.
if your classes are called ball and player then do something like:
// Player.h
class player;
#include "ball.h"
class player{
...
ball* m_ball; //ok
};
---<snip>---
//Ball.h
class ball;
// all includes AFTER the forward declaration
#include "player.h"
class ball{
...
player* m_player; //ok
};
if your classes are called ball and player then do something like:
// Player.h
class player;
#include "ball.h"
class player{
...
ball* m_ball; //ok
};
---<snip>---
//Ball.h
class ball;
// all includes AFTER the forward declaration
#include "player.h"
class ball{
...
player* m_player; //ok
};
I believe his main problem is multiple inclusion. That''s what is messing up his design. BlackEye, your ideas were correct from the beginning, forward declaration is only neccecary when you want two classes in the SAME header to share pointers. When they are in seperate files, this is no longer an issue.
Simply do like this, in each header, before the includes, before EVERYTHING include these lines
#ifdef HEADER_MACRO_WHATEVER // can be the filename if you want#define HEADER_MACRO_WHATEVER// Here goes all header code, classes, structs, whatever#endifPut that in both your headers and it will work without forward declaration. Oh and don''t forget the endif in the end, heh.
Author
Thanks guys , the forward declarations got it.
The #ifdef HEADER_MACRO_WHATEVER etc seems to raise errors in the cpp files. Not to worry if the forward declarations start failing i will figure out why.
Thanks guys, your all great!
The #ifdef HEADER_MACRO_WHATEVER etc seems to raise errors in the cpp files. Not to worry if the forward declarations start failing i will figure out why.
Thanks guys, your all great!
Why is the player controlling the physics of the ball?
You should have a seperate physics class or physics functions, to be doing this for you.
You should have a seperate physics class or physics functions, to be doing this for you.
ARG! I misspelled dammit! That''s why it raises errors, just please try instead of writing #ifdef as the first line, do #ifndef (see the letter ''n'' in there?)
Sorry, my mistake.
Also, the technique I presented fixes another error; multiple inclusion. If you put that in each header, each header can be included by virtually an infinite number of other headers. That''s quite a nifty thing.
TIP: If you are using any version of MSVC you can replace all of that with a simple
#pragma once
statement at the TOP of each header file. It is faster than the standard #ifndef statements, but it works only on MSVC compilers as far as I know.
Sorry, my mistake.
Also, the technique I presented fixes another error; multiple inclusion. If you put that in each header, each header can be included by virtually an infinite number of other headers. That''s quite a nifty thing.
TIP: If you are using any version of MSVC you can replace all of that with a simple
#pragma once
statement at the TOP of each header file. It is faster than the standard #ifndef statements, but it works only on MSVC compilers as far as I know.
This topic is closed to new replies.
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