Friend function c pdf

In objectoriented programming, a friend function, that is a friend of a given class, is a function that is given the same access as methods to private and protected data a friend function is declared by the class that is granting access, so friend functions are part of the class interface, like methods. A friend function can be friendly to 2 or more classes. A class can have public members and private members. If a base class has a friend function, then the function doesnt become a friend of the derived classes.

One class memmber function can access the private and protected members of other class. Here, friend function func is declared inside distance class. The major difference is that a friend function is called like fx, while a member function is called like x. A canonical example is that of types that can be printed to output streams e. Friend function is used when we need to operate on data of. In such situations, we define the function as a friend function with these classes. Now, lets see how we can perform operator overloading by nonmember friend function using pointers.

The friend function can access private and protected data members. To declare a function as a friend of a class, precede the function prototype in the class definition with keyword friend as follows. Friend functions allow alternative syntax to use objects, for instance fx instead of. We can also have a member function of a class to be friend of certain other class. Friend functions and classes are not inherited friend function cannot have storageclass specifier i. The duplicate function is a friend of class rectangle.

Overloading binary minus operator using pointer and friend function. In the last example, you saw how we used a friend function to perform operator overloading, which passed an object by value to the friend function. If a function is friend function of a class, that friend function is not the actual member of the class. If a function is defined as a friend function then, the private and protected data of a class can be accessed using the function the complier knows a given function is a friend function by the use of the keyword friend for accessing the data, the declaration of a friend function should be made inside the body of the class can be anywhere inside class either in. Notice though that neither in the declaration of duplicate nor in its later use in main, function duplicate is considered a member of class rectangle.

So, the private data can be accessed from this function. Friend function must be declared with friend keyword. Friend functions can access private and protected data of the class. Friend function cannot call with the help of object of that class, it is call by using normal c function. Friend function is defined or declared using keyword friend before the function prototype inside the class. Your function implementation should also reside in the project namespace just declaring that you are using it is not enough, the function itself is global if you dont specify it as such and then wont be able to access the members since it is friended in the wrong namespace scope. By using the keyword friend compiler knows the given function is a friend function.

Friend function access the class variable x by using dot operator. An overloaded leftshift operator function, which is often a friend, is needed to achieve seamless streaming capabilities. A true template declaration must precede the friend declaration. Also, in other situations we would like many classes to share a particular function. This function can only be implemented as a nonmember or friend function. Though this example gives you what idea about the concept of friend function.

Member functions and friend functions are equally privileged 100% vested. In the above example, we could have made display as a member function of the class instead of declaring it as a friend function to the class. A friend function of a class is defined outside that class scope but it has the right to access all private and protected members of the class. For example, your friend function really could and maybe should be declared as. To make a nonmember function friend of a class, its declaration needs to be made inside the class and it has to be preceded by the keyword friend. Cs202 6 2 intro to operator overloading copy constructors, issues of memberwise copy constant objects and constant member functions friend functions when to define operators as members vs.

By using friend functions,the member function of one class can be accessed by. Friend function will be defined outside the class without specifying the class name. A friend can be a function, function template, or member function, or a class or class. Friend function like friend class, a friend function can be given special grant to access private and protected members. You can do everything you might want to do without using the friend feature. Any friend function is preceded with friend keyword. A friend function is a nonmember function that grants access to classs private and protected members. It does not have the class scope as it depends on functions original definition and declaration. If a friend declaration in a nonlocal class first declares a class or function the friend class or function is a member of the innermost enclosing namespace.

Friend functions are those functions which can access the. But which function has rights to access to all private and protected members variables and functions. To make a function as a friend of a class, it is declared inside the class either in private or in public section with keyword friend before its declaration as follows. A friend function may be declared friend of more than one class. We simply declare the function within the class by a prefixing its declaration with keyword friend. Friend function will be invoked like normal function, without any object. They are considered to be a loophole in the object oriented programming concepts, but logical use of them can make them useful in certain cases.

The declaration of friend function should be made inside the body of class can be anywhere inside class either in private or. Even though the prototypes for friend functions appear in the class definition, friends are not member functions. What are some advantagesdisadvantages of using friend. However, situations may arise in which it is desirable to allow the explicit access to private members of class to other functions. It takes objects as parameter and access their private members using object name and dot. The following example shows a point class and a friend function, changeprivate. A friend can be a function, function template, or member function, or a class or class template, in which case the entire class and all of its members are friends. The nonmember function has to grant an access to update or access the class. A friend declaration constitutes a use of the template, not a declaration of the template. Friend function can access private data members of the class.

Therefore, function duplicate is able to access the members width and height which are private of different objects of type rectangle. This would allow us to pass the object by reference to the friend function and. Generally, friend function can take object as a argument. From within that function we have been able to access the members length and width, which are private members. Thus the ability to choose between member functions x. This is needed when we want to allow a particular class to access the private and protected members of a class. Friend function must be declare in all the classes from which we need to access private or protected members. The friend function has access to the private data member of the point object it receives as a parameter. A friend function is a nonmember function of the class that has been granted access to all private members of the class. Other members of node class friend int linkedlistsearch. But friend function to the class can access the private members. Oop purists have criticized this feature as weakening the principles of encapsulation and information hiding. Following are some important points about friend functions and classes.