Question

Here is the situation. I have two classes inside two different files.

A.cpp:

#include "B.h" 
A::A(){
B foo; //B doesn't name a type
}

B.cpp:

Class B{
//code
};

How do I correctly construct an object of B inside A’s constructor?(scoping issue) I tried

B::B foo //wrong

and why I can’t directly construct an object of class B like I did above, B.h has been included. Thank you very much

Answer 1

Put the class definition of B into the header file:

b.h:

#ifndef H_B_CLASS
#define H_B_CLASS

class B
{
    // member declarations
};

#endif

a.cpp:

#include "a.h"
#include "b.h"

A::A() { B foo; /* ... */ }

b.cpp:

#include "b.h"

// B's member definitions

If there’s nothing in class B, you can omit b.cpp and put the entire class definition into the header file.