Friend Function using Operator Overloading in C++

Introduction

  • Friend function using operator overloading offers better flexibility to the class.
  • These functions are not a members of the class and they do not have 'this' pointer.
  • When you overload a unary operator you have to pass one argument.
  • When you overload a binary operator you have to pass two arguments.
  • Friend function can access private members of a class directly.
Syntax:
friend return-type operator operator-symbol (Variable 1, Varibale2)
{
     //Statements;
}

Example : Program demonstrating Unary operator overloading using Friend function

#include<iostream>
using namespace std;
class UnaryFriend
{
     int a=10;
     int b=20;
     int c=30;
     public:
         void getvalues()
         {
              cout<<"Values of A, B & C\n";
              cout<<a<<"\n"<<b<<"\n"<<c<<"\n"<<endl;
         }
         void show()
         {
              cout<<a<<"\n"<<b<<"\n"<<c<<"\n"<<endl;
         }
         void friend operator-(UnaryFriend &x);      //Pass by reference
};
void operator-(UnaryFriend &x)
{
     x.a = -x.a;     //Object name must be used as it is a friend function
     x.b = -x.b;
     x.c = -x.c;
}
int main()
{
     UnaryFriend x1;
     x1.getvalues();
     cout<<"Before Overloading\n";
     x1.show();
     cout<<"After Overloading \n";
     -x1;
      x1.show();
      return 0;
}


Output:
Values of A, B & C
10
20
30

Before Overloading
10
20
30

After Overloading
-10
-20
-30

In the above program, operator – is overloaded using friend function. The operator() function is defined as a Friend function. The statement -x1 invokes the operator() function. The object x1 is created of class UnaryFriend. The object itself acts as a source and destination object. This can be accomplished by sending reference of an object. The object x1 is a reference of object x. The values of object x1 are replaced by itself by applying negation.
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