Not able to access private member through friend function

Question

#include <iostream>
using namespace std;

class S;

class R {
        int width, height;
        public:
        int area ()   // Area of rectangle
   {return (width * height);}
    void convert (S a);  
};
class S {
   private:
   int side;
   public:
   S (int a) : side(a) {}
   friend void convert(S a);

};

void R::convert (S a) {    
   width = a.side;
   height = a.side;    // Interpreting Square as an rectangle
}
int main () {

   int x;

   cin >> x;
   R rect;
   S sqr (x);
   rect.convert(sqr);
   cout << rect.area();
   return 0;
}

I am getting the following errors:

prog.cpp: In member function ‘void R::convert(S)’: prog.cpp:26:14: error: ‘int S::side’ is private within this context width = a.side; ^~~~ prog.cpp:16:8: note: declared private here int side; ^~~~ prog.cpp:27:15: error: ‘int S::side’ is private within this context height = a.side; // Interpreting Square as an rectangle ^~~~ prog.cpp:16:8: note: declared private here int side; ^~~~

I tried putting the friend function function private also but same error. Please help

friend is in S class not in R ... – Ankur Jyoti Phukan Mar 18 '17 at 13:55 — Ankur Jyoti Phukan, Mar 18 '17 at 13:55

score 0 · Accepted Answer · answered Mar 18 '17 at 13:57

0

in class S you should have friend R;

friend void convert(S a); is meaningless because the compiler doesn't even know convert belongs to R not S.

answered Mar 18 '17 at 13:57

AlexG

1,091
7
15

Thanks for the solution :) – ujjwal chaudhary Mar 18 '17 at 14:07

score 0 · Answer 2 · answered Mar 18 '17 at 14:06

For starters the name S is not declared before it is first used in the declaration

void convert ( S a);

And secondly you have to specify that the function convert is a member function of the class R.

Try the following

class R {
        int width, height;
        public:
        int area ()   // Area of rectangle
   {return (width * height);}
    void convert ( class S a);  
                   ^^^^^^
};
class S {
   private:
   int side;
   public:
   S (int a) : side(a) {}
   friend void R::convert(S a);
              ^^^ 
};

Not able to access private member through friend function

2 Answers2