Session Objectives Define Static data member Static member functions in a class Object as Function Argument Friend Function Friend Class

FRIEND FUNCTIONS Why it is used? - The concept behind the encapsulation and data hiding restrict the non-member function from accessing the private members of the class. The best way to access a private data member by a non- member function is to change a private data member to a public. but it violates the whole concept of data hiding and encapsulation. To solve this problem friend functions are used when we can access the private or protected members.

Friend informs the compiler that the function is not a member func.Of the class. Syntax : friend func_name(arguments); Member FunctionFriend Function It is a part of class definition and is invoked by a particular object It is no a part of a class It can access the data depending upon whether the function is private or protected It can access any data irrespective of the private or public or protected access

#include class book { private : int bno; char bname[20]; public: void getdata(); friend void show(book); }; void book::getdata() { cin>>bno>>bname; } void show(book bk) { cout<<bk.bno<<bk.bname; } void main() { book b; clrscr(); b.getdata(); show(b); getch(); }

FRIEND FUNCTIONS To access the private member of the class inside the friend function the object of the class should be passed as an argument to the function #include class second; class first { private : int no; public: first(int n); friend int add(first,second); }; class second {

private : int n1; public: second(int); friend int add(first,second); }; first ::first(int n) { no=n; } second ::second(int n) { n1=n; } int add(first f,second s) { cout<<"First class="<<f.no<<endl; cout<<"Second class=“ <<s.n1; return f.no+s.n1; } void main() { first f(10); second s(20); clrscr(); cout<<"\n The Result is "<<add(f,s); }

FRIEND CLASS The private members of one class can be accessed from the member functions Of another class by making them as friends #include class second; class first { private : int no; public: friend class second; first(int n) {

no=n; }}; class second { public: void show(first f) { cout<<f.no; } }; void main() { first f(10); second s; s.show(f); getch(); }

 The friend function acts as a bridge between two objects of different classes which can access even the private members of the class  A friend class is a class whose members functions are all friend functions of another class

EXERCISES  Define “friend “ keyword & its use?  Difference between friend function and member functions?  Explain the use of friend function?  Discuss about friend class?