This document discusses different types of constructors in C++, including default, parameterized, and copy constructors. It provides examples of how to define each type of constructor and demonstrates their usage when creating objects. Destructors are also covered, along with an overview of their purpose to destroy objects and free allocated memory. Constructor overloading and the use of the "this" keyword in C++ are further explained with additional examples.

1. Constructor & Destructors in C++
• Constructor Definition
• Types of Constructor
• Default Constructor
• Parameterized Constructor
• Copy Constructor
By
Prof. Sandeep Vishwakarma

8. Types of Constructors
• Default Constructor
• Parameterized Constructor
• Copy Constructor

10. #include <iostream.h>
#include <conio.h>
class Employee
{
public:
Employee()
{
cout<<"Default Constructor Invoked"<<endl;
}
};
int main(void)
{
Employee e1; //creating an object of Employee
Employee e2;
getch();
}

17. #include<iostream.h>
#include<conio.h>
class Employee
{
public:
int id;
string name;
float salary;
Employee(int i, string n, float s)
{
id = i;
name = n;
salary = s;
}
Parameterized Constructor Example

18. void display()
{
cout<<id<<" "<<name<<" "<<salary<<endl;
} };
int main()
{
Employee e1 =Employee(101, "Sandeep",12000);
Employee e2=Employee(102, "Amit", 15000);
e1.display();
e2.display();
getch();
}

20. When Copy Constructor is called
• When we initialize the object with another
existing object of the same class type. For
example, Student s1 = s2, where Student is
the class.
• When the object of the same class type is
passed by value as an argument.
• When the function returns the object of the
same class type by value.

21. #include<iostream.h> Copy Constructor Example
#include<conio.h>
class A
{
public: int x;
A(int a) // parameterized constructor.
{
x=a;
}
A(A &i) // copy constructor
{
x = i.x;
} };
int main()
{
A a1(20); // Calling the parameterized constructor.
A a2(a1); // Calling the copy constructor.
cout<<a2.x;
getch(); }

24. Thank You

25. Constructor in C++
• Destructor in C++
• Constructor Overloading
• Constructor Overloading Example
• This Keyword
• Hands on Example
By
Prof. Sandeep Vishwakarma

27. Rules for Destructors
• Destructor is a type of special member function of a
class.
• It is used to destroy the memory allocated by the
constructor.
• It has the same name as the class prefixed with a tilde
(~) sign.
• Destructor does not take any arguments and cannot
return or accept any value.
• It is called automatically by the compiler when the
object goes out of scope.
• Compiler calls the destructor implicitly when the
program execution is exited.

33. Example - 1 Constructor Overloading
class Student
{
public:
int rollno;
string name;
Student(int x) // first constructor
{
rollno = x;
name = "None";
}

34. Student(int x, string str) // second constructor
{
rollno = x;
name = str;
}};
int main()
{
Student A(10);
Student B(11, "John");
getch();
}

35. Example - 2 Constructor Overloading
#include <iostream.h>
#include <conio.h>
class ABC
{
private:
int x,y;
public:
ABC () //constructor 1 with no arguments
{
x = y = 0;
}
ABC(int a) //constructor 2 with one argument
{
x = y = a;
}

36. ABC(int a, int b) //constructor 3 with two argument
{
x = a;
y = b;
}
void display()
{
cout << "x = " << x << " and " << "y = " << y << endl;
} };
int main()
{
ABC cc1; //constructor 1
ABC cc2(10); //constructor 2
ABC cc3(10,20); //constructor 3
cc1.display();
cc2.display();
cc3.display();
getch(); }

37. this Keyword
this is a keyword that refers to the current
instance of the class. There can be 3 main
usage of this keyword in C++.
• It can be used to pass current object as a
parameter to another method.
• It can be used to refer current class
instance variable.
• It can be used to declare indexers.

38. Example: this Keyword
#include <iostream.h>
#include <conio.h>
class Employee
{
public:
int id; //data member (also instance variable)
string name; //data member(also instance variable)
float salary;
Employee(int id, string name, float salary)
{
this->id = id;
this->name = name;
this->salary = salary;
}

39. void display()
{
cout<<id<<" "<<name<<" "<<salary<<endl;
} };
int main(void)
{
Employee e1 =Employee(101, “Amit", 12000);
Employee e2=Employee(102, "Nakul", 15000);
e1.display();
e2.display();
getch();
}

40. Thank You