2/6/2009
Object-Oriented Design
CP-419
Lecture # 1
Introduction
The longest journey begins with the first step!
And you should have already traveled a few
miles from home!
(You should know something about
object-oriented programming before starting
this course.)
2
1
2/6/2009
Things you should already know
‣ How to program in some O-O language like Java, C#, or Ruby
‣ One can write horrible programs in an O-O language as easily
as you can in a procedural language
‣ How to work as part of a team to build a non-trivial software
system
‣ Tools used by poor programmers only help them write bad
programs faster
3
What is OO good for???
‣ Constructing software
‣ Reusability
‣ Reliability
‣ Robustness
‣ Extensibility
‣ Distributability
‣ Storability
‣ Maintaining software
‣ Using software
‣ GUI’s are often implemented through object orientation
‣ Managing software projects
4
2
2/6/2009
What is analysis and design
‣ Analysis emphasizes an investigation of the problem rather than how a
solution is defined.
‣ Design emphasizes a logical solution, how the system fulfills the
requirements
‣ Division between A & D is fuzzy
‣ A & D activities exist on a continuum
‣ Some practitioners can classify an activity as analysis, while others put it
into design category.
More analysis oriented
More design oriented
•What
•Requirements
•investigation of domain
•understanding of problem
•How
•logical solution
•understanding and
description of solution
5
What is O-O analysis and design?
‣ The essence of O-O A&D is to consider a problem domain and logical
solution from the perspective of objects (things, concepts, or entities)
‣ O-O Analysis emphasizes finding and describing the objects – or conceptsin the problem domain
‣ O-O Design emphasizes defining logical software objects (things, concepts,
or entities) that have attributes and methods
6
3
2/6/2009
Object vs. function oriented analysis
7
Things to do before starting
‣ Select your language
‣ Select your development environment
‣ Plan your schedule so you have time each week for course work
‣ Purchase the book (the authors / publishers thank you)
8
4
2/6/2009
An object has…
‣ State
‣ Changes over time
‣ Behavior
‣ What the object does in response to messages
‣ Identity
‣ What makes the object unique
9
State
Dave
Age: 32
Height: 6’ 2”
Brett
Age: 35
Height: 5’ 10”
Gary
Age: 61
Height: 5’ 8”
10
5
2/6/2009
Behavior
Get the mail.
Cook dinner.
11
Identity
Okay, which one of
you wise guys is
the real Poppini?
I am the
great
Poppini!
I’m the
I am the
great
Poppini.
De great
Poppini at-a
your service.
No, I’m the great
Poppini.
great
Poppini!
12
6
2/6/2009
Classes
‣ Define the properties and behavior of objects
‣ Can have behavior and properties that are
defined in the class but are independent of
the individual objects
Inheritance
Dad’s smile
Dad’s sports
obsession
Mom’s eyes
Mom’s love
of ROCK
14
7
2/6/2009
Polymorphism
‣ Different type of objects can respond to the same message
‣ The actual method that executes is not determined until run time
‣ Dynamic (or late) binding
15
Encapsulation
…Two… Three.
And
Abracadabra, the
rabbit is gone!
Wait. How’d he do
that? Where’s the
bunny gone?
16
8
2/6/2009
Acknowledgements
While preparing this course I have greatly benefited from the material
developed by the following people:
‣ Dr. Ying ZHOU, Univeristy of Sydney, Australia
‣ Mr. Umair Javed, LUMS, Pakistan
‣ Gary Pollice, David West and Brett D. Laughlin
17
9