C ++ nested classes, variable fathers access

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This question already has an answer here:

  • Can inner classes access private variables? 4 answers

The title already says a lot,

but basically what i want to do is the following(Example):

I have a class called A, and another class inside a called B, like so:

class A
{
   int a;

   class B
   {
      void test()
      {
         a = 20;
      }
   };
};

As you can see my goal is for class B to have access to class A, as it is a nested class. Not this wont work, because B doesn't have access to A, but how can it get access?

Thank You


Despite that you declared class B inside of A, classes A and B are still completely independent. The only difference is that now to refer to B, one must do A::B.

For B to access A's stuff, you should use composition or inheritance. For composition, give B a reference to an object of A, like so:

class B {
public:
  B(const A& aObj) : aRef(aObj) {
    cout << aRef.a << endl;
  }
private:
  const A& aRef;
};

For inheritance, something like this:

class B: public A { // or private, depending on your desires
  B() {
    cout << a << endl;
  }
}