Question

I’ve got the following classes:

class A {
    // Whatever
};

class B {
    T attribute;
    A a;
};

Now suppose i have the following scenario:

A aX, aY;  
B bX, bY;  

Now i can sort of “insert” aX or aY into bX or bY.

I would like for the objects of type A to know, what B they are in, or in other words, what is the “attribute” of their “superclass” B.

Question:

I would like to be able to move the objects of type A freely between their “superclasses” B and i need a way to leak the attribute of B to them dynamically at runtime, so the objects of type A always know, what B they belong to (or what is the attribute of B they are currently in).

What is the best way to do it ?

Answer 1

Perhaps this is useful (pointer from the owner to the attribute, and the reverse):

class A;

class B {
    T attribute;
    A* a;
public:
   void setA(A* newA);
   T getAttribute() {return attribute;}
   void setAttribute() {/*some code*/}
};

class A {
   B* Owner;
   friend void B::setA(A* newA);
public:
    void setOwner(B* newOwner) {
        newOwner->setA(this);
    }
};

void B::setA(A* newA)
{
    A* tempA = this->a;
    B* tempB = newA->Owner;

    tempA->Owner = NULL;
    tempB->a = NULL;

    this->a = newA;
    newA->Owner = this;
}

UPDATED: Fixed a bug in cycle-pointing and cycle-calling, it could be solved only with a friend function.