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.

  1. // sum of two numbers using the friend function
  3. #include<iostream.h>
  4. #include<conio.h>
  6. class B; //declre class b
  8. class A
  9. {
  10. private:
  11. int a; // private data
  12. public:
  13. void setData() // member function
  14. {
  15. cout<<"Enter 1st number: ";
  16. cin>>a;
  17. }
  18. friend void sum(A ob1,B ob2); //declare friend function
  19. };
  20. class B
  21. {
  22. private:
  23. int b; //private data
  24. public:
  25. void setData() // member function
  26. {
  27. cout<<"Enter 2nd number: ";
  28. cin>>b;
  29. }
  30. friend void sum(A ob1,B ob2); // declare friend function
  31. };
  32. void sum(A ob1,B ob2)
  33. {
  34. int s=ob1.a+ob2.b; //accessing private data
  35. cout<<"sum: "<<s<<endl;
  36. }
  38. void main()
  39. {
  40. clrscr();
  41. A obj1;
  42. B obj2;
  43. obj1.setData();
  44. obj2.setData();
  45. sum(obj1,obj2); //invoking the friend function
  46. getch();
  47. }

Friend Function In C++

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.