Question

I have included the proper

Header Files ,
Header Gard

but i cannot instantiate a specific class

Getting Error

error C2065: 'ClassName' : undeclared identifier



Sample Code

Class A{

 //instantiate class B

}


Class B {


 //need to instantiate Class A

}

Answer 1

Since you haven’t posted any real code for us to actually make use of, I’ll take a guess as to what your code actually looks like:

A.h:

#ifndef HEADER_A
#define HEADER_A

#include "B.h"
class A {
private:
  B someMember;
};

B.h:

#ifndef HEADER_B
#define HEADER_B
#include "A.h"

class B {
public:
  doSomething(A param);
};

B.cpp:

#include "B.h"
#include "A.h"

void B::doSomething(A param) { }

As Flinsch said, you need to have forward declarations to avoid problems with include ordering. The simplest way is to get rid of the circular includes in the .h files and just include the forward declarations (class B; and class A; into A.h and B.h) instead.