Q:

Static method with a field

I am currently integrating lua with C++. For lua I need static methods which I've put in a class. I need the static method communicating (save data) with some fields in the class, but it fails when I try different ways. It goes like this:
class CClass{
private:
    static int a;

public:
    static int f();
}

and I try to implement the f() method in this manner:
int CClass::f() {
    a = 5;
    return 0;
}

but it gives me error with unresolved external symbol. How to force the method to save my data in there?
Thanks.

A:

Most static members need to be defined outside the class:
class CClass { 
    static int a;
    // ...
};

int CClass::a;    // in the .cpp file, not the header

