Friend Function In C++

This blog demonstrates friend function in C++. Private members of a class cannot access outside the class but using the friend function it is possible.

Introduction

In this blog, we will learn about friend function in the C++ language. In object oriented programming language private members cannot access from outside the class. In this situation friend function plays a major role.

What is friend function?

A function that accesses private members of a class but is not itself a member of class is called friend function.

Characteristics of a friend function

• It is not declared as a member of any class.
• It is invoked like a normal function using the friend keyword.
• It can access the private members of a class using the object name.
• It has the objects as arguments.

Example

This example shows how to access private members of a class using the friend function.

// sum of two numbers using the friend function

#include<iostream.h>
#include<conio.h>

class B; //declre class b

class A
{
    private:
        int a;   // private data
    public:
        void setData()   // member function
        {
            cout<<"Enter 1st number: ";
            cin>>a;
        }
        friend void sum(A ob1,B ob2); //declare friend function
};
class B
{
    private:
        int b; //private data
    public:
        void setData()       // member function
        {
            cout<<"Enter 2nd number: ";
            cin>>b;
        }
        friend void sum(A ob1,B ob2);  // declare friend function
};
void sum(A ob1,B ob2)
{
    int s=ob1.a+ob2.b; //accessing private data
    cout<<"sum: "<<s<<endl;
}

void main()
{
    clrscr();
    A obj1;
    B obj2;
    obj1.setData();
    obj2.setData();
    sum(obj1,obj2); //invoking the friend function
    getch();
}

In this blog, I will try to explain how to access private data of a class using the friend function in C++ language. Thanks for reading.