Static Member Function in C++

The static keyword is used with a variable to make the memory of the variable static once a static variable is declared its memory can’t be changed. To know more about static keywords refer to the article static Keyword in C++.

Static Member in C++

Static members of a class are not associated with the objects of the class. Just like a static variable once declared is allocated with memory that can’t be changed every object points to the same memory. To know more about the topic refer to a static Member in C++.

Example:

class Person{
     static int index_number; 
};

Once a static member is declared it will be treated as same for all the objects associated with the class.

Example:

C++

// C++ Program to demonstrate
// Static member in a class
#include <iostream>
using namespace std;

class Student {
public:
    // static member
    static int total;

    // Constructor called
    Student() { total += 1; }
};

int Student::total = 0;

int main()
{
    // Student 1 declared
    Student s1;
    cout << "Number of students:" << s1.total << endl;

    // Student 2 declared
    Student s2;
    cout << "Number of students:" << s2.total << endl;

    // Student 3 declared
    Student s3;
    cout << "Number of students:" << s3.total << endl;
    return 0;
}

Output

Number of students:1
Number of students:2
Number of students:3

Static Member Function in C++

Static Member Function in a class is the function that is declared as static because of which function attains certain properties as defined below:

• A static member function is independent of any object of the class. 
• A static member function can be called even if no objects of the class exist.
• A static member function can also be accessed using the class name through the scope resolution operator.
• A static member function can access static data members and static member functions inside or outside of the class.
• Static member functions have a scope inside the class and cannot access the current object pointer.
• You can also use a static member function to determine how many objects of the class have been created.

The reason we need Static member function:

• Static members are frequently used to store information that is shared by all objects in a class. 
• For instance, you may keep track of the quantity of newly generated objects of a specific class type using a static data member as a counter. This static data member can be increased each time an object is generated to keep track of the overall number of objects.

Example:

C++

// C++ Program to show the working of
// static member functions
#include <iostream>
using namespace std;

class Box
{
    private:
    static int length;
    static int breadth;
    static int height;

    public:

    static void print()
    {
        cout << "The value of the length is: " << length << endl;
        cout << "The value of the breadth is: " << breadth << endl;
        cout << "The value of the height is: " << height << endl;
    }
};

// initialize the static data members

int Box :: length = 10;
int Box :: breadth = 20;
int Box :: height = 30;

// Driver Code

int main()
{

    Box b;

    cout << "Static member function is called through Object name: \n" << endl;
    b.print();

    cout << "\nStatic member function is called through Class name: \n" << endl;
    Box::print();

    return 0;
}

Output

Static member function is called through Object name: 

The value of the length is: 10
The value of the breadth is: 20
The value of the height is: 30

Static member function is called through Class name: 

The value of the length is: 10
The value of the breadth is: 20
The value of the height is: 30