Question

HI,

In C++ inner class,

class A {
    public: 
         void f1();
    private:
         void f2();
    class B {
       private void f3(); 
    };

 }

Does an inner class (B) has a pointer to its parent class (A)? (like it does in Java).
And can B calls its parent class public/private method (like it does in Java).

Thank you.

Answer 1

No — in C++, nesting classes only affects names and visibility, not the semantics of the class itself. As far as generated code goes, the nested class is no different from one that isn’t nested.

All that’s changed is the visibility and the name (e.g. if it’s in a private: section of the outer class, it’s not visible to the outside world, and if it’s in a public: section, it’s visible, but (of course) to name it you use outer_class::inner_class. It’s still a completely separate class though — just for example, you can create an instance of the inner class without creating any instance of the outer class.

Edit: Sorry, I missed part of your question. In C++ 0x, the inner class does have access to the the private parts of the outer class — in essence, it’s as if the outer class has declared the inner class as its friend, so private names are visible, but you still need to pass it something like a reference to an object of the outer class before it can invoke any non-static member functions of the outer class.

Although this isn’t supposed to be the case yet, I believe most compilers implement this particular part already.