unresolved external symbol in class

Question

I have been trying for hours to get rid of my errors but it won't go away, i have looked up other posts but nothing seems to work.

I got my .H file with something like this:

using namespace std;   

     class common
    {
    public:
     common();

      static double common::s_a;
      static double common::s_b;

Then i got a .CPP file where i've defined those variables like this:

#include "common.h"

common::common()
{
  common::s_a = 100;
  common::s_b = 100;
}

Then i got this error message(actual variable name instead of a)

common.obj : error LNK2001: unresolved external symbol "public: static double common::s_playerMaxHealth" (?s_playerMaxHealth@common@@2NA)

EDIT : The problem is static, if i remove static i don't have the error anymore. However i need to use static for it to work as intented.

Possible duplicate of [What is an undefined reference/unresolved external symbol error and how do I fix it?](https://stackoverflow.com/questions/12573816/what-is-an-undefined-reference-unresolved-external-symbol-error-and-how-do-i-fix) — user0042, Sep 30 '17 at 22:30
Your assignments for the static variables should not be in the constructor. Instead, they should be at the same scope the class was defined, in this case it's the global namespace. — Jonesinator, Sep 30 '17 at 22:33

score 0 · Accepted Answer · answered Sep 30 '17 at 22:32

You must define these variables like so (in your .cpp file, outside of any function):

double common::s_a;
double common::s_b;

This is a declaration (not a definition):

class common
{   
  static double common::s_a;
  static double common::s_b;

This is a use (not a definition either):

common::common()
{
  common::s_a = 100;
  common::s_b = 100;
}

1 Answers1