C++ Member class declaration in one file. Implementation in another

Question

I would like to know if the process I'll explain below is considered as being standard c++ 98.

In fact, I have an A class that has a private member class called B. To have everything easier to read and more logical, I want to have the declaration of my A class in A.h and of my B class in B.h. As well, I want the implementation of my A class to be in A.cpp and my implementation of my B class in B.cpp.

Below are the files I used to have everything compiled (without any problem) under VS2012 and GCC. I didn't include the inclusion guards in the .h files here for readability reasons.

Thanks in advance for your help.

---------------------------- A.h --------------------------------------------

class A
{
public:
    A();
    void printFromB();
    void createB();
private:
    class B;
    B* b;
};

#include "B.h"

---------------------------- B.h --------------------------------------------

#include <iostream>

class A;

class A::B
{
public:
    void print();
};

---------------------------- A.cpp --------------------------------------------

#include "A.h"

A::A(){}

void A::printFromB() {
    b->print();
}

void A::createB(){
    b = new B;
}

---------------------------- B.cpp --------------------------------------------

#include "A.h"

using namespace std;

void A::B::print()
{
        cout << endl << "B prints!" << endl;
}

-------------------------- main.cpp ------------------------------------------

#include "A.h"

int main()
{
    A a;
    a.createB();
    a.printFromB();

    return 0;
}

Answer 1

There is nothing illegal about your code.

By definition you will never use class B without class A.

But then it is that very definition which asks the question, "Then why bother creating a separate file?" Since this is your project though, you do it how you want.