Question

I have class A such that:

class A {
    static int i;
    A();
    f1();
    f2();
    static void intitiaize();
    // snipped rest
}

void initialize() {
  A::i = 0;
}

in a header file.

I have a intiialize function for the class which initializes the
static variables in main method in second file. After this i create
an object of A to call a.f1().

When I try to create another object of A in file three the compiler complains
saying “no reference to class A”. So included the header in this third file.

I get an error about multiple definitions of A.

How should I proceed? I have include guards around the class file.

Answer 1

You want a declaration of A::i in the header (and you can get rid of your initialize():

//whatever.h:
class A{
    static int i;
    A();
    f1();
    f2();
    ...
}; // don't forget the semicolon on the end.

Then you need a definition of the variable in one CPP file:

// whatever.cpp:
int A::i = 0;

Then include the header wherever you’re going to use objects of the class, and just compile the .CPP file and link it with the others that use this class.