Constructor and Destructor
● A class constructor is a special member function of a class that is executed whenever we
create new objects of that class.
● A constructor will have exact same name as the class and it does not have any return type
at all, not even void.
● Constructors can be very useful for setting initial values for certain member variables.
There are three types of constructor in c++. They are:
1. Default Constructor.
2. Parametrized Constructor.
3. Copy Constructor.
Default constructor
Default constructor is the constructor which doesn't take any argument. It has no parameter.
Syntax:
class_name ()
{
//constructor definition
}
Example:
int main(){
Cube c;
cout<<c.side;
}class Cube
{
public:
int side;
Cube()
{
side=10;
}
};
Output: 10
Parameterized constructor
These are the constructors with parameter. Using this Constructor you can provide different
values to data members of different objects, by passing the appropriate values as argument.
Syntax:
Class_name (arg1,arg2,…)
{
//constructor code
}
Example:
#include<iostream.h>
#include<conio.h>
class Cube{
public:
int side;
Cube(int x)
{
side=x;
}
};
int main()
{
Cube c1(10);
Cube c2(20);
Cube c3(30);
cout<<c1.side;
cout<<c2.side;
cout<<c3.side;
}
Output:
10
20
30
Copy Constructor
These are special type of Constructors which takes an object as argument, and is used to copy
values of data members of one object into other object.
Syntax:
class_name (class_name &ref)
{
//code
}
Example:
#include<iostream.h>
#include<conio.h>
class A{
int a,b;
public:
A(int x, int y)
{
a=x;
b=y;
}
A(A &ref) //copy constructor
{
a=ref.a;
b=ref.b;
}
void show()
{
Cout<<a<<” ”<<b<<endl;
}
};
void main()
{
A obj1(10,20);
A obj2=obj1;
obj1.show();
obj2.show();
getch();
}
Destructor
● Destructor is used to destroy the object that have been created by a constructor .
● Destructor can never take any argument and it does not return any value.
● Invoked implicitly by the program to cleanup the storage.
Syntax:
~ destructor_name()
{
}
Example:
#include<iostream.h>
#include<conio.h>
int count=0;
class alpha{
public:
alpha(){
count++;
cout<<”no of object created”<<count;
}
~alpaha(){
cout<<”no of object destroyed”<<count;
count--;
}
};
void main()
{
alpha A1,A2,A3;
}
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