Question

I have class A. And I have class B. And I have many-many classes derived from class B.

I want to achieve this: derivatives of B should have access to the protected variables of A. Whithout each of them containing an instance of A, which would need a lot of memory.
So I guess public inheritance is not a good idea this time. How do I solve this?
Thanks!

Answer 1

You could do it with friend and accessor functions. This does trust B to stay off A‘s privates – don’t see a good way to let only B and subclasses access only protected members of A unless there’s an inheritance relationship between A and B.

class A {
friend class B;
protected:
  int X;
};


class B {
protected:
  static int getX(A const & a) { return a.X; }
};

class C : public B {
public:
  void foo(A const & a) { int bar = getX(a); }
};