Q. 4. What is a friend function in OOP? write a program in C++ to swap value of two different classes using the friend function?

 

Q. 4. What is a friend function in OOP? write a program in C++ to swap value of two different classes using the friend function? 

Sol. 

What is Friend Function?

A friend function is a function that is declared outside a class but is capable of accessing the private and protected members of the class.

Program to swap values of classes using friend function

/*WRITE A PROGRAM TO SWAP PRIVATE DATA MEMBER OF TWO DIFFERENT CLASSES USING FRIEND FUNCTION*/

#include<iostream.h>

#include<conio.h>

class class_2;

class class_1

{ 

 int value1;

 public: 

 void indata(int a) 

 { 

  value1=a; 

 } 

 void display(void) 

 { 

  cout<<value1<<"\n"; 

 } 

 friend void exchange(class_1 &, class_2 &);

};

class class_2

{ 

 int value2;

 public: 

 void indata(int a) 

 { 

   value2=a; 

 } 

 void display(void) 

 { 

  cout<<value2<<"\n"; 

 } 

 friend void exchange(class_1 &, class_2 &);

};

void exchange(class_1 &x, class_2 &y)

{ 

 int temp = x.value1; 

 x.value1 = y.value2; 

 y.value2 = temp;

}

int main()

{ 

 class_1 C1; 

 class_2 C2;

 C1.indata(100); 

 C2.indata(200); 

 cout<<"Values before exchange"<<"\n";

 C1.display(); 

 C2.display(); 

 exchange(C1, C2); 

 cout<<"Values after exchange"<<"\n"; 

 C1.display(); 

 C2.display(); 

 return 0;

}

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OUTPUT:-