Include loops
Author
I am writing an upgradable encapsulation of everything. Don''t ask why. I guess I am a bit obsessive, or maybe I have a complex. Who knows?
Well, anyway, I have one class called clsUniverse in clsUniverse.h and .cpp. Another class called clsObject is in clsObject.h and .cpp.
clsObject can be stripped down to this:
class clsObject
{
public:
friend clsUniverse; //I hope this is legal - tell me
private:
bool exists;
clsUniverse* the_universe; //the one that it "exists" in
}
clsUniverse can be stripped down to this:
class clsUniverse
{
public:
void Create (clsObject& an_object);
// an_object.the_universe = this;
}
the clsObject.h file needs to include clsUniverse.h, but clsUniverse.h needs to include clsObject.h. That would mean they would keep including each other infinitely. How do I overcome this problem?
I could do something like this:
clsUniverse.h-
#include "clsObject.h"
clsObject.h-
#ifndef _CLSUNIVERSE_H_
#include "clsUniverse.h"
#endif
Is there any other solution?
#pragma once
Although the method of defining a variable to mark inclusion of the header file is the most common (and compiler independent).
BTW a small aside if you are using the #define method, don''t put any underscore at the front of the symbol you''re using. Symbols which begin with underscores followed by a capital letter are reserved by both the C and C++ standards for compiler and SDK use. If you use names with underscores, don''t complain if you ever get a namespace conflict.
--
Simon O''''Connor
Creative Asylum Ltd
www.creative-asylum.com
Although the method of defining a variable to mark inclusion of the header file is the most common (and compiler independent).
BTW a small aside if you are using the #define method, don''t put any underscore at the front of the symbol you''re using. Symbols which begin with underscores followed by a capital letter are reserved by both the C and C++ standards for compiler and SDK use. If you use names with underscores, don''t complain if you ever get a namespace conflict.
--
Simon O''''Connor
Creative Asylum Ltd
www.creative-asylum.com
Forward declarations.
In clsObject.h (btw are you a VB programmer?):
And then in clsUniverse.h:
The downside to forward declarations is that you cannot reference any properties (data members) or operations (methods) of the class. The name is essnetially declareed as a placeholder.
In clsObject.h (btw are you a VB programmer?):
class clsUniverse; // this is a forward declarationclass clsObject{ ...}; And then in clsUniverse.h:
class clsObject;class clsUniverse{ ...}; The downside to forward declarations is that you cannot reference any properties (data members) or operations (methods) of the class. The name is essnetially declareed as a placeholder.
So long as it is only a complex, you are doing fine. The day it becomes a quaternion, seek medical advice. 
Each of your header file should be structured that way :
Since your whole header file is bracketed by the #ifndef/#endif statements, any #include statement beyond the first will only add whitespaces to the file being processed.
Or, as Oluseyi said, if you only need to declare pointers/references/arguments, you can use a forward declaration.
The problem with #pragma is that they are compiler-specific.
Each of your header file should be structured that way :
#ifndef HEADER_FILE_H#define HEADER_FILE_H...#endif /* HEADER_FILE_H */ Since your whole header file is bracketed by the #ifndef/#endif statements, any #include statement beyond the first will only add whitespaces to the file being processed.
Or, as Oluseyi said, if you only need to declare pointers/references/arguments, you can use a forward declaration.
The problem with #pragma is that they are compiler-specific.
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