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Basic Concepts of Object Orientation

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Basic Concepts of Object Orientation Object-Oriented Analysis CIM2566 Bavy LI – PowerPoint PPT presentation

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Title: Basic Concepts of Object Orientation


1
Basic Concepts of Object Orientation
  • Object-Oriented Analysis
  • CIM2566
  • Bavy LI

2
What is Object-Orientation?
  • Object-orientation is the use of objects and
    classes in analysis, design, and programming.
  • The use of objects distinguishes
    object-orientation from other techniques such as
  • traditional structured methods (process-based
    data and function are separate)
  • knowledge based systems (logic programming
    Prolog)
  • mathematical methods (functional programming
    Scheme).

3
Why did OO Arise?
  • Modeling in analysis and software design and
    languages for programming originally focused on
    process. But many results indicated the process
    approach was problematic and led to the software
    crisis.
  • Hierarchical Functional Decomposition
  • Top-Down Design (TDD)
  • What are the advantages/disadvantages of TDD?

4
Why does Organization need Object-Orientation?
  • Organizationally, OO provides a superior means
    of
  • Problem/Business Analysis and Requirements
  • Better Software Development/Modern programming
    practice
  • Superior Software Engineering Metrics
  • Web Presence and Utilization
  • Software Reuse
  • Software Use
  • Enterprise Engineering

5
Terminology 1
  • OOA Object Oriented Analysis
  • analyzing your problem by decomposition into
    objects
  • OOD Object Oriented Design
  • designing your code into objects
  • OOP Object Oriented Programming
  • programming using the concepts of object
    orientation

6
Terminology 2
  • Class
  • a design (like a blueprint for a house) of an
    object that contains data and methods
  • Object
  • an instance (like a particular house with a
    street address) of a class with a unique identity
  • Abstraction
  • only exposing the important, relevant qualities
    of an object or system

7
Terminology 3
  • Attribute
  • a named property of an object capable of holding
    state, as similar as instance variables or data
    members
  • Method
  • an operation on an object, also called a function
    or operation

8
What are the Primary Object-Oriented Languages
Today?
  • C added classes to C as early as 1985
  • A hybrid object-oriented languages with powerful
    features including multiple inheritance,
    exceptions, templates, operator overloading etc
  • Java was created as a simplification of C that
    could run on any machine, providing a
    write-once/run anywhere capability.
  • EJB 2.0 is the new standard for the J2EE, or Java
    2 Platform, Enterprise Edition

9
What are the Primary Object-Oriented
Methodologies Today?
  • The Unified Modeling Language, or UML, has become
    the industry standard design and analysis
    notation, which lends itself to a methodology.

10
What are the Benefits Of Object-Orientation?
  • Reuse, quality, an emphasis on modeling the real
    world, a consistent OOA/OOD/OOP package,
    naturalness (our "object concept"), resistance to
    change, encapsulation and abstraction, and etc.
  • On resistance to change, system objects change
    infrequently while processes and procedures
    (top-down) are frequently changed.

11
Big Three (and a half)
  • The three and a half key ingredients of OOP are
  • Encapsulation,
  • Inheritance,
  • Polymorphism, and
  • Message Passing

12
Encapsulation
  • hides implementation, shows only interface
  • "Encapsulation is the process of hiding all of
    the details of an object that do not contribute
    to its essential characteristics." Booch

13
Inheritance
  • IS A relationship
  • A new class can be created by "Inheriting" from
    another class or multiple classes.
  • The new class inherits methods and data members
    of the "parent" class.
  • This is also called "extending" the base class,
    or "sub-classing".

14
Message Passing
  • a message is an invocation of a method on an
    object
  • "an object-oriented program is a bunch of objects
    laying around sending messages to one another."

15
Polymorphism
  • the ability to hide many different
    implementations behind a single interface. When
    objects respond differently to the same message
    this is a form of Polymorphism.
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