Nested Class member function can't access function of enclosing class. Why?

Question

Please see the example code below:

class A
{
private:
    class B
    {
    public:
        foobar();
    };
public:
    foo();
    bar();
};

Answer 1

This is an automagic, albeit possibly nonportable trick (worked on VC++ since 6.0 though). Class B has to be a member of class A for this to work.

#ifndef OUTERCLASS
#define OUTERCLASS(className, memberName) \
    reinterpret_cast(reinterpret_cast(this) - offsetof(className, memberName))
#endif 

class A
{
private:
    class B
    {
    public:
        void foobar() {
           A* pA = OUTERCLASS(A, m_classB);
           pA->foo();
        }
    } m_classB;
public:
    foo();
    bar();
};