C++ 43: Creating Objects Dynamically

 Pointer and Object:

if required we can store address of an object in the pointer

Syntax: class_name *ptr_name = & object_name;

Accessing object members by using pointer:

If the pointer is pointing to an objetct then the members of the object can be access by using following way:

Syntax:

        1) ptr_name = member_name

        2) (*ptr_name)member_name

Example:

//Pointer and Object
#include <iostream>
#include <string.h>
using namespace std;
class Student
{
private:
    int RN;
    char N[20], D[20];
public:
    Student(int rn, char n[], char d[])
    {
        RN = rn;
        strcpy(N, n);
        strcpy(D, d);
    }
    void showData()
    {
        cout << "Roll No: " << RN << endl;
        cout << "Name: " << N << endl;
        cout << "Department: " << D << endl;
    }
};
int main()
{
    Student a(111, "Jack", "CSE");
    Student *p;
    p = &a;
    // pointer to object
   (*p).showData();
    p->showData();
    return 0;
}

Output:

Roll No: 111
Name: Jack
Department: CSE
Roll No: 111
Name: Jack
Department: CSE

Creating objects dynamically / Dynamic Initialization of object / Pointer to object

• The object is created dynamically then, we can destroy the object at runtime if the object is no more required.
• The object can be create and dynamically as follows:

To create object dynamically- class_name *ptr_name = new class_name(val 1,val2, ...);

To destroy object dynymically - delete ptr_name;

#include <iostream>
#include <string.h>
using namespace std;
class Student
{
private:
    int RN;
    char N[20], D[20];
public:
    Student(int rn, char n[], char d[])
    {
        RN = rn;
        strcpy(N, n);
        strcpy(D, d);
    }
    void showData()
    {
        cout << "Roll No: " << RN << endl;
        cout << "Name: " << N << endl;
        cout << "Department: " << D << endl;
    }
};
int main()
{
    // Student a(111, "Jack", "CSE");
    // a.showData();
    // Student b(112, "JAmes", "IT");
    // b.shoeData();
    // Student c(113, "William", "CSE");
    // c.showData();
    Student *p = new Student(111, "Jack", "CSE"); //Reserving mrmory
    p->showData();
    delete p;                            //Relesing memory
    p = new Student(112, "James", "IT"); //Reserving mrmory
    p->showData();
    delete p; //Relesing memory
    return 0;
}

Output:

Roll No: 111
Name: Jack
Department: CSE
Roll No: 112
Name: James
Department: IT