Program Of Friend Function In C++

#include<iostream.h>

#include<conio.h>

class test

{

private:

int a,b;

public:

void getdata(int x,int y)

{

a=x;

b=y;

}

friend void display(test);

}       ;

void  display(test t2)

{

cout<<"\n a="<<t2.a;

cout<<"\n b="<<t2.b;

}

main()

{

clrscr();

test t1;

t1.getdata(8,9);

display(t1);

getch();

}

..............................................................................................................

A friend function for a class is used in object-oriented programming to allow access to public, private, or protected data in the class from the outside. Normally, a function that is not a member of a class cannot access such information; neither can an external class. Occasionally, such access will be advantageous for the programmer. Under these circumstances, the function or external class can be declared as a friend of the class using the friend keyword.

A friend function is declared by the class that is granting access. Friend declaration can be placed anywhere in the class declaration. It is not affected by the access control keywords.

A similar concept is that of friend class.

Friends should be used with caution. Too many functions or external classes declared as friends of a class with protected or private data may lessen the value of encapsulation of separate classes in object-oriented programming and may indicate a problem in the overall architecture design.


VIEW SOURCE:- http://en.wikipedia.org/wiki/Friend_function