OOP ProgrammingMelick R. Baranasooriyamelick-rajee.blogspot.com

Principles of OOP

Abstraction

Encapsulation Polymorphism

Inheritance

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Inheritance

Loyalty

Member

Staff

Gold

RegularNon Member

4

Classes and Interfaces

Classes

Fields, properties, methods

Methods contain code for

execution

Interfaces

methods and properties, left to be implemented

later

5

Inheritance

characteristics of existing parent class

extend the parent class

Add new fields and methods

AttributesOperations

Redefine methods 6

Inheritance

inherits

implements Extends

Extensibility

Reusability

Provides abstraction

Eliminates redundant code 7

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Accessibility Levels

protected internal - limited to the current assembly or types

derived from the containing class

Protected - limited to the containing type and types derived from it

Internal - limited to the current assembly

Private -restricted to the containing type

Public –access is not

restricted 9

Important Aspects

Instance and static constructors are not inherited

Multiple interfaces can be implemented

Structures cannot be inherited

No multiple inheritance

Transitive relationC < - B , B < -A

then C <-A 10

Demo

Sealed

Methods + New Multiple Interfaces

Virtual + Override

Access Modifiers11

Abstraction – Reducing the complexity

Classes defined with the keyword abstract

Implemented or fully unimplemented

Not implemented methods are

declared abstract

Class + Interface

Cannot be instantiated 12

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Encapsulation

Hides the implementation details

All data members should be hidden

Accessed via properties

Public interface

No interface members should

be hidden 14

Encapsulation ..

Private data fields

Changing the class internals does not affect

Change fields validation

Constructors and Assessors

Reduces complexity

Easier maintenance

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Polymorphism Cohesion and Coupling

Having many forms

Virtual Keyword

Override Keyword

Extensibility

Reusability

Provides abstraction

Eliminates redundant code 16

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THANK YOU! 18