Count the number of objects using Static member function in C++ Program

C++Server Side ProgrammingProgramming

The goal here is to count the number of objects of a class that are being created using a static member function.

A static data member is shared by all objects of the class commonly. If no value is given, a static data member is always initialized with 0.

A static member function can only use static data members of that class.

We are using a class Student here. We will declare a static data member count which will store the count of objects. A static member function rollCall(void) which will display the count of objects as roll no.s of students in a class.

Approach used in the below program is as follows

  • We declare a class Student which has public data members int rollno and static data member count.

  • There is a constructor which calls rollcall() and initializes rollno with count.

  • There is a destructor which decreases count.

  • Static member function rollcall() displays the count of objects as Student count and increments the count.

  • Each time the object of Student is created, constructor calls rollcall() and count is incremented. This count is assigned to rollno of that Student object.

  • In the main we created 4 objects of class Student as stu1,stu2,stu3,stu4 and verified that count and rollno is the same as no. of objects.

Example

 Live Demo

// C++ program to Count the number of objects
// using the Static member function
#include <iostream>
using namespace std;
class Student {
public:
   int rollno;
   static int count;
public:
   Student(){
      rollCall();
      rollno=count;
   }
   ~Student()
   { --count; }
   static void rollCall(void){
      cout <<endl<<"Student Count:" << ++count<< "\n"; //object count
   }
};
int Student::count;
int main(){
   Student stu1;
   cout<<"Student 1: Roll No:"<<stu1.rollno;
   Student stu2;
   cout<<"Student 2: Roll No:"<<stu2.rollno;
   Student stu3;
   cout<<"Student 3: Roll No:"<<stu3.rollno;
   Student stu4;
   cout<<"Student 4: Roll No:"<<stu4.rollno;
   return 0;
}

Output

If we run the above code it will generate the following output −

Student Count:1
Student 1: Roll No:1
Student Count:2
Student 2: Roll No:2
Student Count:3
Student 3: Roll No:3
Student Count:4
Student 4: Roll No:4
raja
Published on 29-Aug-2020 11:55:02
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