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General and Gameplay Programming Programming

Started by FrigidHelix March 18, 2002 07:39 PM

6 comments, last by FrigidHelix 22 years, 1 month ago

FrigidHelix

122

Author

March 18, 2002 07:39 PM

I have no idea why this isn''t working, since I have done something like it before, but each time I try to access a static member, i get the following link error:

quote:error LNK2001: unresolved external symbol "public: static long CFraction::MaxNumerator" (?MaxNumerator@CFraction@@1JA)

Here is a stripped down version of the class I am using. It is defined in a header file.

  class CFraction
{
protected:	
	long	Numerator;
	long	Denominator;
public:
	
	CFraction() { Numerator=Denominator=1;}

	static long MaxNumerator;
	static long MaxDenominator;
};

Now, in my main cpp file I try and set the static member MaxNumerator using the following code:

  long CFraction::MaxNumerator = 10L;

And, as aforementioned, I get a linker error. Any ideas?

Jindocai

122

March 18, 2002 07:51 PM

I can''t seem to be able to repeat the link error.

Might I suggest you post your entire code (for both CFraction.h, main.cpp and if you have it CFraction.cpp (or where ever you define your CFraction functions).

Anonymous

March 18, 2002 09:29 PM

the static variable must not be in main.cpp (i think)

btw, put your code here

Dragonskin

122

March 18, 2002 09:59 PM

The only thing I can think of is that you are setting the value before the header file is included (if it is included at all).

FrigidHelix

122

Author

March 22, 2002 09:13 PM

I created a test project, below is its entire code. This is ridiculous!!! WHY THE #%^#$# won't this work? I copied the code almost exactly from a C++ book (Practical C++)

    #include <iostream.h>class myClass{public:	static int var;	static void setVar( int i )	{		var = i;	}};int main(){	// Doesnt work. I get the compiler error:	// definition or redeclaration illegal in current scope	int myClass::var = 1;	// Compiles, but I get linker error:	// unresolved external symbol 	// "public: static int  myClass::var" (?var@myClass@@2HA)	myClass::setVar( 1 );	return 0;}

[edited by - FrigidHelix on March 22, 2002 10:14:17 PM]

Anonymous

March 22, 2002 09:22 PM

It would seem that you forgot to define the static member. Here is the template for using a static member:

  // header file ''SomeClass.h''class SomeClass{public:// stuffprivate:static int i;// stuff};// implementation file ''SomeClass.cpp''#include "SomeClass.h"int someClass::i=0;    // Initialize to a value is optional// driver file ''MyProg.cpp''#include <iostream>using namespace std;#include "SomeClass.h"int main(){SomeClass::i=5;cout << someClass::i;return 0;}

-D

Anonymous

March 22, 2002 09:31 PM

Clarification -- Initializing to a value in the implementation file is optional. Defining there is not. So it has to be in one of the following two forms:

int SomeClass::i=0;

or

int SomeClass::i;

Sorry for the poor formatting of my code example in the previous post. I am still getting used to the interface.

-D

FrigidHelix

122

Author

March 23, 2002 01:35 AM

thanks a lot. I finally understand my fault: I need to move the definition of the static variable outside of any functions. It was in fact an incorrect scope. thanks guys.

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