Access Protected Members of a enclosing class [Nested Classes]

Question

I got the following code:

class enclosing{
protected:
    int var1 = 2;
    int var2 = 4;
public:
    class problem{
    friend enclosing;
    public:
        void DoStuff(enclosing&e1){
            int Sum = e1.var1 + e1.var2;
        }
    }i1;
}e1;

My question is, how do i access the protected member variables of the enclosing class? Is this even Legal?

Related: http://stackoverflow.com/questions/3058267/nested-class-member-function-cant-access-function-of-enclosing-class-why?rq=1 — EdChum, May 06 '15 at 13:17
No it's not. You need to provide the inner class an instance of an enclosing class to work on. — Luchian Grigore, May 06 '15 at 13:17

score 1 · Accepted Answer · answered May 06 '15 at 13:31

You have your friendship backwards - a class can't declare itself to be friend of somebody else.

Unlike in Java's "inner classes", a class defined within a class does not automatically have access to an instance of the class the defines it - the "inner" class is completely independent, and you need to pass it the instance you want it to work with.

Like so:

class enclosing
{
protected:
    int var1 = 2;
    int var2 = 4;
public:
    friend class problem;
    class problem
    {
    public:
        void DoStuff(enclosing& e){
            int Sum = e.var1 + e.var2;
        }
    } i1;
} e1;

int main()
{
    e1.i1.DoStuff(e1);
    enclosing e2;
    e2.i1.DoStuff(e1); // Also works
    enclosing::problem x;
    x.DoStuff(e2); // This, too.
}

Thanks for the detailed explaination – DVSProductions May 06 '15 at 13:34 — DVSProductions, May 06 '15 at 13:34

score 0 · Answer 2 · answered May 06 '15 at 13:26

0

The data members have to be accessed via an object of the enclosing class. For example

void DoStuff( const enclosing &e){
            int Sum = e.var1 + e.var2;
        }

answered May 06 '15 at 13:26

Vlad from Moscow

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Thanks man, you made my day. Finally a good solution after searching for an hour – DVSProductions May 06 '15 at 13:30

Access Protected Members of a enclosing class [Nested Classes]

2 Answers2