4.Constructor.pptx for oops programming language

Dr.J.saira banu , Associate Professor, SCOPE, VIT University
Constructors

Constructors
Classes control object initialization by defining one or more
special member functions known as constructors.
The job of a constructor is to initialize the data members of a
class object.
A constructor is run whenever an object of a class type is
created.
Constructors have the same name as the class.
Unlike other functions, constructors have no return type.
Constructors can not be virtual.

Constructors
•A class can have multiple constructors.
•Like any other overloaded function, the constructors
must differ from each other in the number or types of
their parameters.
•Constructors are the special type of member functions
that initializes the object automatically when it is
created.
•Compiler identifies that the given member function is a
constructor by its name

Constructor - Syntax
class classname {
public:
//Declaring the default constructor.
classname() {
}
};

Types of constructors
•There are several forms in which a constructor can
take its shape namely:
•Default Constructor
•Parameterized Constructor
•Copy Constructor

Default constructor
•Classes control default initialization by defining a
special constructor, known as the default constructor.
The default constructor is one that takes no arguments.
•If the class does not explicitly define any constructors,
the compiler will implicitly define the default
constructor.
•The compiler-generated constructor is known as the
synthesized default constructor.

Default constructor – Example1
int main()
{
math o;
o.add();
return 0;
}
Dr.J.saira banu , Associate Professor, SCOPE, VIT
University
class math
{
private:
int a,b,c;
public:
math()
{
a=0;
b=0;
}
void add()
{
c=a+b;
cout<<"Total : "<<c;
}
};

Default constructor -Example
#include <iostream>
using namespace std;
class Base {
public: int square;
Base(int x = 5) // Default constructor with a default value.
square = x * x;
}
void show() {
cout << "Square of number =" << square << endl;
}
};
int main() {
Base b;
b.show();
return 0; }

Parameterized constructor
•A parameterized constructor is the one that has
parameters or arguments specified in it.
•We can pass the arguments to constructor function
when object is created.
•A constructor that can take arguments is called
parameterized constructor.
•When a constructor is parameterized, we must pass
the initial values as arguments to the constructor
function when an object is declared.

Parameterized constructor -Syntax
class classname {
public:
//Declaring the default constructor.
classname( int, int ) {
}
};
Classname objname(list of parameters);

Parameterized constructor -example
• class math
• {
• private:
• int a,b,c;
• public:
• math(int x,int y)
• {
• a=x;
• b=y;
• }
• void add()
• {
• c=a+b;
• cout<<"Total : "<<c;
• }
• };
University
• int main()
• {
• math o(10,25);
• o.add();
• return 0;
• }

Copy constructor
• A copy constructor is a member function which initializes an object
using another object of the same class. It is used to declare and
initialize an object from another object.
• The most common form of copy constructor is shown here:
• classname (const classname &obj)
• { // body of constructor }
• Here, obj is a reference to an object that is being used to initialize
another object.
• Copy constructor object creation:
• integer (integer & i) ; (or)
• integer I 2 ( I 1 ) ; (or)
• integer I 2 = I 1 ;

Copy constructor
• The copy constructor creates an object by initializing it with an object
of the same class, which has been created previously.
• The copy constructor is used to:
• Initialize one object from another of the same type.
• Copy an object to pass it as an argument to a function.
• Copy an object to return it from a function.
• The process of initializing through a copy constructor is known as copy
initialization.
• A reference variable has been used as an argument to the copy
constructor as we cannot pass the argument by value to a copy
constructor

Copy Constructor Example
• class math
• {
• private:
• int a,b,c;
• public:
• math(int x,int y)
• {
• a=x;
• b=y;
• }
• math(math &x1)
• {
• a=x1.a;
• b=x1.b;
• }
• void add()
• {
• c=a+b;
• cout<<"Total : "<<c<<endl;
• }
• int main()
• {
• math o(10,25);
• math o1(o);
• o.add();
• o1.add();
• return 0;
• }
University

Destructors
• A destructor is a special member function of a class that is executed
whenever an object of it's class goes out of scope.
• A destructor will have exact same name as the class prefixed with a
tilde (~).
• It can neither return a value nor can it take any parameters.
• Destructor can be very useful for releasing resources before coming
out of the program like closing files, releasing memories etc.
• The destructor is commonly used to "clean up" when an object is no
longer necessary

Destructors
•Destructors are called when one of the following
events occurs:
•An object allocated using the new operator is explicitly
deallocated using the delete operator.
•A local (automatic) object with block scope goes out of
scope.
•The lifetime of a temporary object ends.
•A program ends and global or static objects exist.

Destructor syntax

Destructor Example

4.Constructor.pptx for oops programming language

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