Static Member Function in C++

The static is a keyword in the C and C++ programming language. We use the static keyword to define the static data member or static member function inside and outside of the class. Let's understand the static data member and static member function using the programs.

Static data member

When we define the data member of a class using the static keyword, the data members are called the static data member. A static data member is similar to the static member function because the static data can only be accessed using the static data member or static member function. And, all the objects of the class share the same copy of the static member to access the static data.

Syntax

Here, the static is a keyword of the predefined library.

The data_type is the variable type in C++, such as int, float, string, etc.

The data_member is the name of the static data.

Example 1: Let's create a simple program to access the static data members in the C++ programming language.

#include <iostream>
#include <string.h>
using namespace std;
// create class of the Car
class Car
{
private:
int car_id;
char car_name[20];
int marks;

public:
// declare a static data member
static int static_member;

Car()
{
static_member++;
}

void inp()
{
cout << " \n\n Enter the Id of the Car: " << endl;
cin >> car_id; // input the id
cout << " Enter the name of the Car: " << endl;
cin  >> car_name;
cout << " Number of the Marks (1 - 10): " << endl;
cin >> marks;  
}

// display the entered details
void disp ()
{
cout << " \n Id of the Car: " << car_id;
cout << "\n Name of the Car: " << car_name;
cout << " \n Marks: " << marks;

} 
};

// initialized the static data member to 0
int Car::static_member = 0;

 int main ()
{
// create object for the class Car
Car c1;
// call inp() function to insert values
c1. inp ();
c1. disp();

//create another object
Car c2;
// call inp() function to insert values
c2. inp ();
c2. disp();


 cout << " \n No. of objects created in the class: " << Car :: static_member <<endl;
return 0;
}

Output

Enter the Id of the Car: 
101
Enter the name of the Car: 
Ferrari
Number of the Marks (1 - 10): 
10

Id of the Car: 101 
Name of the Car: Ferrari 
Marks: 10

Enter the Id of the Car: 
205
Enter the name of the Car: 
Mercedes
Number of the Marks (1 - 10): 
9

Id of the Car: 205 
Name of the Car: Mercedes 
Marks: 9
No. of objects created in the class: 2

Static Member Functions

The static member functions are special functions used to access the static data members or other static member functions. A member function is defined using the static keyword. A static member function shares the single copy of the member function to any number of the class' objects. We can access the static member function using the class name or class' objects. If the static member function accesses any non-static data member or non-static member function, it throws an error.

Syntax

Here, the class_name is the name of the class.

function_name: The function name is the name of the static member function.

parameter: It defines the name of the pass arguments to the static member function.

Example 2: Let's create another program to access the static member function using the class name in the C++ programming language.

#include <iostream>
using namespace std;
class Note
{
// declare a static data member
static int num;

public:
// create static member function
static int func ()
{
return num;
}
};
// initialize the static data member using the class name and the scope resolution operator
int Note :: num = 5; 

int main ()
{
// access static member function using the class name and the scope resolution
cout << " The value of the num is: " << Note:: func () << endl;
return 0;
} 

Output

The value of the num is: 5

Example 3: Let's create another program to access the static member function using the class' object in the C++ programming language.

#include <iostream>
using namespace std;
class Note
{
// declare a static data member
static int num;

public:
// create static member function
static int func ()
{
cout << " The value of the num is: " << num << endl;	
}
};
// initialize the static data member using the class name and the scope resolution operator
int Note :: num = 15; 

int main ()
{
	// create an object of the class Note
	Note n;
// access static member function using the object
n.func();

return 0;
} 

Output

The value of the num is: 15

Example 4: Let's consider an example to access the static member function using the object and class in the C++ programming language.

#include <iostream>
using namespace std;
class Member
{

private:
// declaration of the static data members
static int A;
static int B;
static int C;

// declare public access specifier
public:
// define the static member function
static void disp ()
{
cout << " The value of the A is: " << A << endl;
cout << " The value of the B is: " << B << endl;
cout << " The value of the C is: " << C << endl;
}
};
// initialization of the static data members
int Member :: A = 20;
int Member :: B = 30;
int Member :: C = 40;

int main ()
{
// create object of the class Member
Member mb;
// access the static member function using the class object name
cout << " Print the static member through object name: " << endl;
mb. disp();
// access the static member function using the class name
cout << " Print the static member through the class name: " << endl;
Member::disp();
return 0;
}

Output

Print the static member through object name:
The value of the A is: 20
The value of the B is: 30
The value of the C is: 40   
Print the static member through the class name:
The value of the A is: 20
The value of the B is: 30
The value of the C is: 40

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