Accessing static class variables in C++?

Question

Duplicate:
C++: undefined reference to static class member

If I have a class/struct like this

// header file class Foo {    public:    static int bar;    int baz;    int adder(); };  // implementation int Foo::adder() {    return baz + bar; } 

This doesn't work. I get an "undefined reference to `Foo::bar'" error. How do I access static class variables in C++?

Answer 1

You must add the following line in the implementation file:

int Foo::bar = you_initial_value_here; 

This is required so the compiler has a place for the static variable.

Answer 2

It's the correct syntax, however, Foo::bar must be defined separately, outside of the header. In one of your .cpp files, say this:

int Foo::bar = 0;  // or whatever value you want