Can 2 classes share a friend function?

Question

Today i have a doubt regarding friend function. Can two classes have same friend function? Say example friend void f1(); declared in class A and class B. Is this possible? If so, can a function f1() can access the members of two classes?

Beseech

Yes it is possible. Yes, f1() would have access to members of both classes. – Concertmaster

Have you tried compiling a simple example? This seems like it would be easy to test. – Teacup

What makes you think this would not be possible? – Cypro

Answer 1

An example will explain this best:

class B;                   //defined later

void add(A,B);

class A{
    private:
    int a;
    public:
    A(){ 
        a = 100;
    }
    friend void add(A,B);
};   

class B{
    private:
    int b;
    public:
    B(){ 
        b = 100;
    }
    friend void add(A,B);
};

void add (A Aobj, B Bobj){
    cout << (Aobj.a + Bobj.b);
}

main(){
    A A1;
    B B1;
    add(A1,B1);
    return 0;
}

Hope this helps!

Kora

Thank you very much man ur example was very nice and easy to understand – Beseech

Answer 2

There is no restriction on what function can or cannot be friends's of class's, so yes there's no problem with this.

Georgetta

Well, you have to be able to name the function, but that's a natural restriction. E.g. struct { static void foo(); }; or functions in anonymous namespaces in other translation units. – Fusco

Answer 3

correction to the above code

#include<iostream>
using namespace std;
class B;                   //defined later
class A;                  //correction (A also need be specified)
void add(A,B);

class A{
    private:
    int a;
    public:
    A(){
        a = 100;
    }
    friend void add(A,B);
};

class B{
    private:
    int b;
    public:
    B(){
        b = 100;
    }
    friend void add(A,B);
};

void add (A Aobj, B Bobj){
    cout << (Aobj.a + Bobj.b);
}

main(){
    A A1;
    B B1;
    add(A1,B1);
    return 0;
}

Austrasia

Answer 4

#include<iostream>

using namespace std;

class first
{
    friend void getdata(first object1, int i);
};

class second
{
    friend void getdata(second object2, int j);
};

getdata(first object1, int i, second object2, int j)
{
    cout<<i+j;
}

main()
{
    first object1;
    second object2;
    getdata(object1, 5, object2, 7);
}

Shifty

friends functions are intended to have access to classes private members – Waken