TYPES OF MEMBER
FUNCTIONS
We already know what member functions are
and what they do. Now lets study some special member functins present in the
class. Following are different types of Member functions,
1.
Simple functions
2.
Static functions
3.
Const functions
4.
Inline functions
5.
Friend functions
Simple Member functions
These
are the basic member function, which dont have any special keyword like static
etc as prefix. All the general member functions, which are of below given form,
are termed as simple and basic member functions.
return_type functionName(parameter_list)
{
function body;
}
Static Member functions
Static is something that holds its position. Static is a
keyword which can be used with data members as well as the member functions. We
will discuss this in details later. As of now we will discuss its usage with
member functions only.
A
function is made static by using static keyword with function name. These
functions work for the class as whole rather than for a particular object of a
class.
It can
be called using the object and the direct member access
. operator. But, its more typical to call a static
member function by itself, using class name and scope resolution :: operator.
Example :
class X
{ public:
static void f(){};
};
int main()
{
X::f(); // calling member function directly with
class name
}
These functions cannot access ordinary data members and member
functions, but only static data members and static member functions.
It doesn't
have any "this" keyword which is the reason it cannot access ordinary
members. We will study about "this" keyword later.
Const Member functions
We will study Const keyword in detail later, but as an
introduction, Const keyword makes variables constant, that means once defined,
there values can't be changed.
When
used with member function, such member functions can never modify the object or
its related data members.
//Basic Syntax of const Member Function
void fun() const {}
Inline functions
All the member functions defined
inside the class definition are by default declared as Inline. We will study
Inline Functions in details in the next topic.
Friend functions
Friend functions are
actually not class member function. Friend functions are made to give private access to non-class
functions. You can declare a global function as friend, or a member function of
other class as friend.
Example :
class WithFriend
{
int i;
public:
friend void fun(); // Global
function as friend
void fun()
{
WithFriend wf;
wf.i=10; // Access to private data member
cout << wf.i;
}
int main()
{
fun(); //Can be called directly
}
Hence, friend
functions can access private data members by creating object of the class.
Similarly we can also make function of other class as friend, or we can also
make an entire class as friend class.
class Other
{
void fun();
};
class WithFriend
{
private:
int i;
public:
void getdata(); // Member function of class WithFriend
friend void
Other::fun(); // making function of
class Other as friend here
friend class Other; // making the complete class as friend
};
When we make a class as friend, all its member functions
automatically become friend functions.
Friend
Functions is a reason, why C++ is not called as a pure Object Oriented
language. Because it violates the concept of Encapsulation.
Thank you friends for reading my blog.
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