Friend Function

Friend Function

•  The friend function is a function that is not a member function of the class but it can access the private and protected members of the class.

•  The friend function is given by a keyword friend.

•  These are special functions which are declared anywhere in the class but have given special permission to access the private members of the class.

C++ Program

#include<iostream>

using namespace std;

class test

{

int data;

friend int fun(int x);//declaration of friend function

public:

test()//constructor

{

    data = 5;

}

};

int fun(int x)

{

    test obj;

    //accessing private data by friend function

    return obj.data + x;

}

int main()

{

    cout << "Result is = "<< fun(4)<<endl;

}

Output

Result is = 9

Properties of Friend Functions

• Following are some properties of friend functions –

 1. The friend function is not defined within the scope of the class.

 2. It can not be invoked by the object of particular class.

3. It can be invoked like a normal function.

4. This function can access the private members of the class.

5. Usually the objects of some class are passed as an argument to the friend function.

6. It must be declared with the keyword friend.

Review Questions

1. Explain in detail about friend functions in C++ with example.

2. Explain friend function with an example.