Object oriented programming

Disclaimer: This presentation is prepared by trainees of baabtra as a part of mentoring program. This is not official document of baabtra – Mentoring Partnerbaabtra – Mentoring Partner is the mentoring division of baabte System Technologies Pvt. Ltd

Object Oriented Programming(OOP)

Arjun P Ajay

Pop-Procedure Oriented Programming Language(Structured programming)

• Structured programming is based around data structures and subroutines

• The subroutines are where stuff actually "happens"• data structures are simply containers for the information

needed by those subroutines.

POP can be briefly summarized as

• No code reusability. Hence time to develop the software and debugging increase.

• As Length of application increases, the programmer loses control over it.

• software designers tend to use Top-Down approach, in which the overall objective of the system is defined first.

• Then the system is divided into various sub tasks or sub modules.

• With this methodology, software development is done by writing a set of sub programs, called functions that can be integrated together to form a complex system.

What is oop

What is oop

OOP allow decomposition of program into a number of entities called objects .

Build data and functions around these objects.

Object consist of data and function.

The data of an object can be accessed only by the functions associated with that object

What is OOP?

• Objects can be used effectively to represent real-world entities

• An object oriented program may be considered a collection interacting object.

• Each object is capable of sending and receiving messages and processing data

Object oriented programming concepts

• Object• Class• Data Abstraction• Modularity• Delegation• Encapsulation • Polymorphism• Inheritance

Class

• A class is the blueprint of an object

• Multiple objects can be created from the same class

• Class is a collection of member data and member functions.

• Objects contain data and code to manipulate that data.

• The entire set of data and code of an object can be made a user-defined data type with the help of a class.

Class members

• Namespace: The namespace is a keyword that defines a distinctive name or last name for the class.

• Class declaration: Line of code where the class name and type are defined.

• Fields: Set of variables declared in a class block.• Constants: Set of constants declared in a class block.• Constructors: A method or group of methods that

contains code to initialize the class.

• Properties: The set of descriptive data of an object.

• Events: Program responses that get fired after a user or application action.

• Methods: Set of functions of the class.• Destructor: A method that is called when the

class is destroyed

Access keywords• Access keywords define the access to class members from the

same class and from other classes• Public: Access to the class member from any other class.

Accessible from outside of the class & assembly– It can access from anywhere– There is no restriction on accessibility• Private: Access to the class member only in the same class. • Protected: Allows access to the class member only within the

same class and from inherited classes. Accessible within class & sub-classes

• Internal: Allows access to the class member only in the same assembly.

• Protected internal: Allows access to the class member only within the same class, from inherited classes

'Imported namespaces Imports System' Namespace: Consider using CompanyName.Product.ComponentType Namespace DotNetTreats.OOSE.OOP_VBNET'Class declaration Public Class employee'FieldsPrivate _name As StringPrivate _salary As Integer'ConstantsPrivate Const anualBonus As Integer = 1000'Constructors Public Sub New()MyBase.New()End Sub

'PropertiesPublic Property Name() As StringGetReturn _nameEnd GetSet(ByVal Value As String)_name = valueEnd SetEnd PropertyPublic Property Salary() As IntegerGetReturn _salaryEnd GetSet(ByVal Value As Integer)_salary = valueEnd SetEnd Property

' Event handlersPublic Event OnPromotion As EventHandler'MethodsPublic Sub DuplicateSalary()_salary = (_salary * 2)End SubEnd ClassEnd Namespace

ByVal is short for "By Value" *it means is that you are passing a copy of a variable to your Subroutine. * You can make changes to the copy and the original will not be altered.

ByRef short for By Reference *you are not handing over a copy of the original variable but pointing to the original

variable.

ObjectsAn object is anything that really exists in the world and can be distinguished from others

Every object has properties and can perform certain actions

These properties are represented by variables in programming and actions are performed by methods (functions). So an object contains variables and methods Objects are the building

blocks of OOP and are commonly defined as variables or data structures

Object composition

• Object identity: Means that every object is unique and can be differentiated from other objects. Each time and object is created (instantiated) the object identity is defined.

• Object behavior: What the object can do. In OOP, methods work as functions that define the set of actions that the object can do.

• Object state: The data stored within the object at any given moment. In OOP, fields, constants, and properties define the state of an object.

Structures

Not everything in the real world should be represented as a class.

• Structures are suitable to represent lightweight objects.

• Structures can have methods and properties and are useful for

• defining types that act as user-defined primitive

Encapsulation• The wrapping up of data and functions into a single unit

(called class) is known as encapsulation.• In OOP we are capsuling our code not in a shell but in

"Objects" & "Classes".• It hides all the internal details of an object from the outside

world• It hides its data and methods from outside the world and only

expose data and methods that are required.• It provides us maintainability, flexibility and extensibility to

our code.• Encapsulation allows developers to build objects that can be

changed without affecting the client code that uses them

• The data is not accessible to the outside world and only those functions which are wrapped in the class can access it.

• These functions provide the interface between the object's data and the program.

• This insulation of the data from direct access by the program is called data hiding.

Data Abstraction

• “The process of identifying common patterns that have systematic variations; an abstraction represents the common pattern and provides a means for specifying which variation to use"

• An abstract class is a parent class that allows inheritance but can never be instantiated

• Abstract classes contain one or more abstract methods that do not have implementation.

• Abstract classes allow specialization of inherited classes.

Data Abstraction contn…

• Abstraction is a powerful means to tackle the complexity of programming by wrapping up and thus reducing the complexity of complex operations.

• In this it display only the features that needed the user, and hide all other data

• Through Abstraction all relevant data can be hide in order to reduce complexity and increase efficiency

Polymorphism• Its the property in which a single object can take more than one form.• Single interface & multiple method is called polymorphism.• Polymorphism allows objects to be represented in multiple forms.• Polymorphism is a concept linked to inheritance and assures that

derived class have the same function even though each derived class performs different operations

Ex:• Function overloading (Static polymorphism / early binding).• Function overriding (dynamic polymorphism / late binding).

• Polymorphism allows a client to treat different objects in the same way even if they were created from different classes and exhibit different behaviors.

Polymorphism

• Method Overloading- Method with same name but with different arguments is

called method overloading.- Method Overloading forms compile-time polymorphism.

• Method Overriding- Method overriding occurs when child class declares a

method that has the same type arguments as a method declared by one of its super class.

- Method overriding forms Run-time polymorphism.

• Modularity-The modularity of object-oriented programming means

that the valid components of a big program can each be implemented individually.

-Different people can work on various classes.-Each execution task is isolated from the others.-A ``module'' is nothing more than a file containing source

code. - Breaking a large (or even not-so-large) program into

different files is a convenient way of splitting it into manageable pieces.

-Each piece can be worked on independently and compiled alone, then integrated with other pieces when the program is linked

Delegation

Delegation allows the behavior of an object to be defined in terms of the behavior of another object.

ie , Delegation is alternative to class inheritance.• Delegation is a way of making object composition as powerful as inheritance. • In delegation, two objects are involved in handling a

request: -A receiving object delegates operations to its delegate. -This is analogous to the child classes sending requests to

the parent classes.

• When an object receives a request, the object can either handle the request itself or pass the request on to a second object to do the work.

• If the object decides to pass the request on, you say that the object has forwarded responsibility for handling the request to the second object.

Inheritance

• Inheritance is the property in which, a derived class acquires the attributes of its base class.

• you can create or 'inherit' your own class (derived class), using an existing class (base class). You can use the Inherits keyword for this.

• In OOP, a parent class can inherit its behavior and state to children classes.

• This concept was developed to manage generalization and specialization in OOP and is represented by a is-a relationship.

*The concept of generalization in OOP means that an object encapsulates common state an behavior for a category of objects. *The general object in this sample is the geometric shape. *Most geometric shapes have area, perimeter, and color.*The concept of specialization in OOP means that an object can inherit the common state and behavior of a generic object; however, each object needs to define its own special and particular state an behavior

The Shape class is the parent class. Square, Rectangle, and Circle are derived classes that inherit from Shape. The triangle-connector in the diagram represents an is-a relationship.

Imports SystemClass Human 'This is something that all humans do Public Sub Walk() Console.Writeline ("Walking") End Sub End Class‘A Programmer is a Human

Class Programmer Inherits Human 'We already have the above Walk() function 'This is something that all programmers do ;) Public Sub StealCode() Console.Writeline ("Stealing code") End Sub End Class

• Example Program for classPublic Class ExamplePrivate _value As Integer Public Sub New()

_value = 2 End Sub

Public Function Value() As IntegerReturn _value * 2

End FunctionEnd Class

Module Module1 Sub Main()

Dim x As Example = New Example()Console.WriteLine (x.Value())

End SubEnd Module -----------(out put =4)

• Program that uses Inherits keyword [VB.NET]

Class A Public _value As Integer

Public Sub Display()Console.WriteLine(_value)

End SubEnd Class

Class B : Inherits A Public Sub New(ByVal value As Integer)

MyBase._value = value End SubEnd Class

Class C : Inherits A Public Sub New(ByVal value As Integer)

MyBase._value = value * 2 End SubEnd Class

Module Module1 Sub Main()

Dim b As B = New B(5)b.Display()

Dim c As C = New C(5)c.Display()

End SubEnd Module

• Imports Systempublic Class Circle Public Radius As Double Public Function CalculateDiameter() As Double Return Radius * 2 End Function

Public Function CalculateCircmuference() As Double Return CalculateDiameter() * 3.14159 End Function

Public Function CalculateArea() As Double Return Radius * Radius * 3.14159 End FunctionEnd Class

Public Class Exercise Public Sub Main() Dim circ As Circle = New Circle circ.Radius = 25.84 Console.WriteLine(" -=- Circle Characteristics -=-") Console.WriteLine("Radius: {0} ", circ.Radius) Console.WriteLine("Diameter:{0} ",circ.CalculateDiameter()) Console.WriteLine("Circumference:{0} ",

circ.CalculateCircmuference()) Console.WriteLine("Area: {0} " & vbCrLf, circ.CalculateArea()) End SubEnd Class

• Result• -=- Circle Characteristics -=-Radius : 25.55Diameter : 51.1Circumference : 160.535249Area : 2050.837805975

• Advantages of OOP

Object-Oriented Programming has the following advantages over conventional approaches:

• OOP provides a clear modular structure for programs which makes it good for defining abstract data types where implementation details are hidden and the unit has a clearly defined interface.

• OOP makes it easy to maintain and modify existing code as new objects can be created with small differences to existing ones.

• OOP provides a good framework for code libraries where supplied software components can be easily adapted and modified by the programmer. This is particularly useful for developing graphical user interfaces.

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