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Friend function

Friend function C++

friend_function_c++

Friend function acts as a friend of the class. It can access the private and protected members of the class. The friend function is not a member of the class, but it must be listed in the class definition. The non-member function cannot access the private data of the class. Sometimes, it is necessary for the non-member function to access the data. The friend function is a non-member function and has the ability to access the private data of the class.

To make an outside function friendly to the class, we need to declare the function as a friend of the class as shown below:

class sample  
{  
   // data members;  
 public:  
friend void abc(void);  
};  

Following are the characteristics of a friend function:

  • The friend function is not in the scope of the class in which it has been declared.
  • Since it is not in the scope of the class, so it cannot be called by using the object of the class. Therefore, friend function can be invoked like a normal function.
  • A friend function cannot access the private members directly, it has to use an object name and dot operator with each member name.
  • Friend function uses objects as arguments.

Let's understand this through an example:

#include <iostream>  
using namespace std;  
class Addition  
{  
 int a=5;  
 int b=6;  
 public:  
 friend int add(Addition a1)  
 {  
     return(a1.a+a1.b);  
 }  
};  
int main()  
{  
int result;  
Addition a1;  
 result=add(a1);  
 cout<return 0;  
}  
Output:
11

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Uk01 on May 24, 2015 at 12:05 am


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