Friend Functions in C++

What is a friend function?

A friend is a function that is not a member of a class, but has access  to the private members of the class.

·        A friend function of a class can be a global function.

·        Access specifier do not apply to the friends of a class.

·        This friendship is unidirectional.

A friend function can access the private and protected data of a class. We declare a friend function using the friend keyword inside the body of the class.

 

Friend Function Syntax:

class className {

    ... .. ...

    friend returnType functionName(arguments);

    ... .. ...

}

Declaration of a friend function in C++

class class_name

{

   friend data_type function_name(arguments/s);   //syntax of friend function.

};

 

Brief Syntax:-

•         friend is a keyword to denote that this function is a friend function.

•         dataType is the function’s data type.

•         Function_Name is the name of the function being made a friend of the class.

•         arg list is the arguments that are passed.

      

Example 1: Friend function declaration

Output:

Mean value: 40

 

Example 2:   Friend function declaration

 

Output:

X=5

Y=2

 

Example 3: Friend function declaration

 

 

Output:

Sum: 25

 

Friend functions of another class by defining the function using the scope resolution operator as shown below:

class class_Name1

{

int function_Name();

};

Class class_Name2

{

 Friend int class_Name1::function_Name();

};

 

Example:

Output:

The value of b is: 12