C++ oop

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Object Oriented Programming
OOP……. Not OOPS!!

2
Object-Oriented Programming Concepts
What is an Object?
What is a Class?
Encapsulation?
Inheritance?
Polymorphism/Dynamic Binding?
Data Hiding?
Data Abstraction?
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Custom Data Type
class Shape {
private:
int borderWidth = 0;
public:
int getBorderWidth() {
return borderWidth;
}
void setBorderWidth(int bw) {
borderWidth = bw;
}
};
:Shape
-color :String
-borderWidth:int
+getColor():String
+setColor()
+getBorderWidth():int
+setBorderWidth()
Members
Member
variables
Member
methods

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Define attribute/variable
 void main(){
 Shape s;
 s.setBorderWidth(3);
 ….
 cout<<s.getBorderWidth();
}
S is an object here

Real World Entities – More Classes
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:Automobile
-color :String
-speed:int
-make:String
+$NO_OF_GEARS
+getColor():String
+setColor()
+getMake():String
+setMake()
+break()
+changeGear()
+accelerator()
+getSpeed():int
:Person
-name:String
-dob : Date
-address:String
+$AVG_AGE
+getName():String
+setName()
+getAdress():String
+setAddress()
+getDob (): Date
+setDob ()
+getAge() : int
:Account
-number:String
-accountType : String
-balance:double
+getNumber():String
+setNumber()
+getAccountType():String
+setAccountType()
+deposit ()
+withdrawal ()
+getBalance():double
+fundTransfer()
+payBill()

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Constructor
class Shape {
public Shape(){
cout<<“This is default
constructor”;
}
};
Shape s;
 Constructor is just like a method.
 It does not have return type.
 Its name is same as Class name.
 It is called at the time of object
calling.
 Constructors are used to initialize
instance/class variables.
 A class may have multiple
constructors with different number
of parameters.

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Multiple Constructors
One class may have more than one constructors.
Multiple constructors are used to initialize different
sets of class attributes.
When a class has more than one constructors, it is
called Constructor Overloading.
Constructors those receive parameters are called
Parameterized Constructors.

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Constructors Overloading
class Shape {
public :
Shape(){
cout<<“This is default
constuctor”;
}
Shape(int a){
cout<<a;
}
Shape s ;
Or
Shape s1(5);

Default Constructor
 Default constructor does not receive any parameter.
o public Shape(){ .. }
 If User does not define any constructor then Default
Constructor will be created by Compiler.
 But if user defines single or multiple constructors then
default constructor will not be generated by Compiler.
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Destructor
It is inverse of constructor function.
It is used to deallocate the memory or
release the resources like closing files.
It is called when object is destroyed.
It has a same name as class name used
tilde(~) as prefix.
~class_name(){…….}
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Copy Constructor
It is a special type of constructor .
It is used to create new object as a copy of
existing object.
It is a standard way to copy an object.
It is used to initialize one object from another
object of the same type.
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Copy Constructor…
class CopyCon{
private :
int a1;
public:
CopyCon(){}
CopyCon(int a){
a1 = a;
}
void display(){
cout<<a1;
}
};
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void main(){
clrscr();
CopyCon c(2);
CopyCon c1 = c;
c.display();
c1.display();
getch();
}

Operator Overloading
Built-in operators can be redefined &
overloaded.
Overloaded operators are functions with special
names.
It is used to perform operations on user defined
data type.
 + operator overloaded on two integer values to
perform addition.
 + operator overloaded on two string values to
perform concatenation.
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return_type operator sign(){}
void operator +() {
count=count+1;
}
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 class temp {
private:
int count;
public:
temp():count(5){ }
void operator ++() {
count=count+1;
}
void Display() {
cout<<"Count: "<<count;
}
};
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int main()
{
temp t;
++t;
t.Display();
return 0;
}

Operators that cannot be overloaded
scope operator - ::
sizeof
member selector - .
member pointer selector - *
ternary operator - ?:
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Scope Resolution Operator ::
It is used to qualify hidden name.
When local variable and global variable are
having same name, local variable gets the
priority.
C++ allows flexibility of accessing both the
variables through a scope resolution
operator.
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int a = 10;
void main(){
o int a = 15;
o cout<<a<<::a;
o ::a=20;
o Cout<<a<<::a;
}
Output :15 10
 15 20
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OOP Key Concepts
Encapsulation:
o Creates Expert Classes.
Inheritance:
o Creates Specialized Classes.
Polymorphism:
o Provides Dynamic behaviour at Runtime.
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Encapsulation
Gathering all related methods and attributes in a
Class is called encapsulation.
Often, for practical reasons, an object may wish
to expose some of its variables or hide some of
its methods.
Access Levels:
Modifier Class Subclass Packag
e
World
private X
protected X X X
public X X X X

Friend Function
There is a mechanism in C++ to access
private & protected members of a class.
This mechanism is known as friend function
or friend class.
We have to use friend keyword in prefix of
function name.
Declaration should be inside the class body
starting with keyword friend.
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 class Distance {
o private:
o int meter;
o public:
o Distance(): meter(0){ }
o friend int func(Distance); //friend function
 };
 int func(Distance d) {//function definition
o d.meter=5; //accessing private data from non-member function
o return d.meter;
 } int main() {
o Distance D;
o cout<<"Distace: "<<func(D);
o return 0;
 }
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Inheritance
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Inheritance
:Shape
color :String
borderWidth:int
getColor():String
setColor()
getBorderWidth():int
setBorderWidth()
:Rectangle
length :int
width:int
area()
getLength()
setLength()
:Circle
radius : int
area()
getRadius()
setRadius()
:Triangle
base:int
hight:int
area()
getBase()
setBase()
Circle c ;
c.getColor();
c.getBorderWidth();
c.area();
UML Notation

Polymorphism
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Polymorphism
One thing with multiple forms.
Two types of polymorphism
Static Polymorphism(Overloading)
Dynamic Polymorphism(Overriding)
Ways to Provide polymorphism:
o Through Interfaces.
o Method Overriding.
o Method Overloading.
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Method Overriding – area()
:Shape
Color :String
borderWidth:int
getColor():String
setColor()
getBorderWidth():int
setBorderWidth()
area()
:Rectangle
length :int
width:int
area()
getLength()
setLength()
:Circle
radius
area()
getRadius()
setRadius()
:Triangle
base:int
hight:int
area()
getBase()
setBase()
Shape s;
s.getColor();
s.getBorderWidth();
s.area();

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Abstract Class
 What code can be written in Shape.area() method?
o Nothing, area() method is defined by child classes. It should have
only declaration.
 Is Shape a concrete class?
o NO, Rectangle, Circle and Triangle are concrete classes.
 If it has only area declaration then
o Class will be abstract.
 Benefit?
o Parent will enforce child to implement area() method.
o Child has to mandatorily define (implement) area method.
o This will achieve polymorphism.

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Shape
class Shape {
private:
int borderWidth = 0;
public :
double area();
int getBorderWidth() {
return borderWidth;
}
};

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Interface / Virtual function
A class is made abstract by declaring at least one
of its functions as pure virtual function
A pure virtual function is specified by placing "= 0"
in its declaration
public:
virtual double area() = 0;

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Interfaces
Richman
earnMony()
donation()
party()
Businessman
name
address
earnMony()
donation()
party()
SocialWorker
helpToOthers()
Businessman
name
address
earnMony()
donation()
party()
helpToOthers()
Businessman
name
address
helpToOthers()

Data Abstraction
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Data Abstraction ( Cont. )
Data abstraction is the way to create complex data
types and exposing only meaningful operations to
interact with data type, whereas hiding all the
implementation details from outside world.
Data Abstraction is a process of hiding the
implementation details and showing only the
functionality.
Data Abstraction in java is achieved by interfaces
and abstract classes.
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Data Hiding
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Data Hiding ( Cont. )
Data Hiding is an aspect of Object Oriented
Programming (OOP) that allows developers
to protect private data and hide
implementation details.
Developers can hide class members from
other classes. Access of class members
can be restricted or hide with the help of
access modifiers.
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Disclaimer
This is an educational presentation to enhance the
skill of computer science students.
This presentation is available for free to computer
science students.
Some internet images from different URLs are
used in this presentation to simplify technical
examples and correlate examples with the real
world.
We are grateful to owners of these URLs and
pictures.
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Thank You!
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C++ oop

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C++ oop