friend class declaration

Question

i am new to c++ programming, can we declare some members of class as friend to other class. it means Lets say Class A have three member functions and instead of declaring whole class as friend to other Class B (say) can i declare only one member of class A as friend to Class B, so please help.

Answer 1

Yes you can declare a single member function as friend of another class.
Online Sample:

#include<iostream>
class Myclass;
class Otherclass
{
    public:
      void doSomething(Myclass &obj);

};
class Myclass
{
    int i;
    friend void Otherclass::doSomething(Myclass &obj);
};
void Otherclass::doSomething(Myclass &obj)
{
    obj.i = 10;
    std::cout<<obj.i;
}


int main()
{
    Myclass obj;
    Otherclass obj2;
    obj2.doSomething(obj);
    return 0;
}

Answer 2

Yes:

class A
{
    public:
        void func_1();
        void func_2();
        void func_3();
};

class B
{
    friend void A::fund_2();
    void plop(); // only A::func_2() can call this function
};

Answer 3

On declaration of a friend class all member functions of the friend class become friends of the class in which the friend class was declared. source

Answer 4

Not to be harsh on you, but look what I found by simply Googling "c++ friend class functions":

Friend Functions And Classes

...and about 200 more.

Answer 5

yes.

For an example, ask wiki (they know everything):

http://en.wikipedia.org/wiki/Friend_function

Or do a basic search ...