Question

Given the following code without considering friendship between two classes:

class OutSideClass
{
...
public:
    int i_pub;
protected:
    int i_pro;
private:
    int i_pri;

    class InSideClass
    {
        ...
        public:
            int j_pub;
        protected:
            int j_pro;
        private:
            int j_pri;
    };
};

Question 1> Is it true that OutSideClass can ONLY access public members of InSideClass

Question 2> Is it true that InSideClass can access all members of OutSideClass

Please correct me if my understanding is not correct.

Answer 1

Question 1> Is it true that OutSideClass can ONLY access public members of InSideClass

Yes

Question 2> Is it true that InSideClass can access all members of OutSideClass

No, in C++03. Yes, in C++11.

---

The Standard text is very clear about this:

The C++ Standard (2003) says in $11.8/1 [class.access.nest],

The members of a nested class have no special access to members of an
enclosing class, nor to classes or functions that have granted
friendship to an enclosing class; the usual access rules (clause 11)
shall be obeyed. The members of an enclosing class have no special
access to members of a nested class; the usual access rules (clause
11) shall be obeyed.

However, the Standard quotation has one defect. It says the nested classes don’t have access to private members of the enclosing class. But in C++11, it has been corrected: in C++11, nested classes do have access to private members of the enclosing class (though the enclosing class still doesn’t have access to private members of the nested classes).

See this Defect Report :

• 45. Access to nested classes