Constructors and its types in C++

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Constructor

• A constructor is used for automatic declaration of an object.
• It has same name as the name of class in which it resides.
• Constructor has no return type, even void.
• If we have not define any constructor then C++ will automatically define it.
• It is used only for initialization and not for input/output.

Syntax :

class class-name
{
private :

data member;

public :

class-name() //constructor defined
}
};

main()
{

class-name object=class-name(); //calling constructor
}


Example :


#include <iostream.h>
#include <conio.h>

class Account
{
private:

int account_no;
char *name;

public :

//defining the constructor Note that class-name and constructor name is same :

Account(char *n,int a)
{
//initializing the variables :

name=n;
account_no=a;
}

void display()
{
cout<< "Name is : "<< name;
cout<< "\nAccount number is : "<< account_no;

}

};

void main()
{
clrscr();

//creating object and calling the constructor :

Account acc=Account("Ashish",111);
acc.display();

getch();

}


Output :








Properties of constructors :

• Constructors not have any return type, even void.
• The constructor can't be virtual.
• The constructor can't be static.
• The name of the constructor is same as that of class.
• Member function can be accessed within a constructor function.
• A constructor initializes all the objects created under class.

Types of Constructors :

There are four types of constructors :

• Default constructor
• Parameterized constructor
  
• Copy constructor
• Dynamic constructor

We will discuss these types in the next topics.

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