Friend Class

                Friend class is also used to access private members of the class in another class. Here we use forward declaration of class.

#include<conio.h>

#include<iostream>

using namespace std;

class square;//Forward declaration of class

class rectangle

{

                int hieght;

                int width;

                public:

                                rectangle(){hieght=0,width=0;}

                                rectangle(int a, int b){hieght=a,width=b;}

                                void convert(square s);// class sqaure is called in the rectangle class.

                                int area()

                                {

                                return hieght*width;

                                }

};

class square

{

                friend class rectangle; //declaring rectangle as a friend class

                int side;

                public:

                                square(int a){side=a;}

                               

};

void rectangle::convert(square s)

{

                hieght=s.side;

                width=s.side;

}

int main()

{

                rectangle rect;

                square sqr(4);

                rect.convert(sqr);

               

                cout<<"area of square :"<<rect.area();

                getch();

                return 0;

               

}


Naveen Dengani

Friend function

                Friend function is used to access private data members of the class. Friend is not a member function but it is declared in the class and defined outside the class. For friend class click on the link.

#include<conio.h>

#include<iostream>

using namespace std;

class avg

{

                private:

                        float a,b;

                public:

                                avg(){a=0.0,b=0.0;}

                                void get()

                                {

                                                cout<<"\n enter the value of a and b: ";

                                                cin>>a>>b;

                                }

                                friend float avrg(avg x); //friend function declaration.

};

float avrg(avg x) // friend definition.

{

                return (x.a+x.b)/2;

}

int main()

{

                avg A;

                A.get();

                cout<<"\n the average value of these two numbers is :"<<avrg(A);

                getch();

                return 0;

}