Object-Oriented

Analysis and Design

How do you write great software every

time?

Great software?

The software must do what the customer wants it to do

Make your code smart

Well-DesignedWell-Coded

Easy to mantain

Easy to reuseEasy to extend

Great software satisfies the customer and the programmer

Programmers are satisfied when:

Their apps can be REUSED Their apps are FLEXIBLE

Customers are satisfied when:

Their apps WORK Their apps KEEP WORKING

Their apps can be UPGRADED

Ok but… what shall the software do?

Gathering requirements

Pay attention to what the system needs to

You can figure out how later

Requirement?

It’s a specific thing

Yoursystemhas to do

towork correctly

Usually a single thing, and you can test that thing to make sure you fullfilled the requirement

The complete app or project you are working on

2 - so if you leave out a requirement or even if they forget to mention sth your system isnt working correctly

1 - The customer decides when a system works correctly,

Your software has a context

Developers viewpoint(the perfect world)

Real world

+ Analysis =

Real world context

Textual analysis = nouns / verbsUse cases

Diagrams

Nothing ever stay the same

No matter how much you like your softwareRight now, it’s probably going to changeTomorrow…

Good design = flexible and resilient design

Design principles

Techniques that can be applied for designing or writing code to make that code more Mantainable, flexible or extensible

OCPOpen-closed

princople

DRYDon’t repeat

yourself

SRPSingle

responsibility principle

Classes are open for extensionAnd closed for modification

Avoid duplicate code by abstractingThings that are common

Every object in your project should have a single responsability

Open-closed principle

class Printer{public final void print(Printable p){

…}

}

class SquarePrinter extends Printer{public void print(Square s){

…}

}OPEN = Extending functionality

ClOSED = NO OVERRIDES

Single responsibility principle

public class MobileCaller{

public void callMobile(MobileNo mobileNo){ ... }}

public class ValidationService{

public static boolean validateMobileNumber(MobileNo mobileNo){ ... }

}

Responsibility #1: Call

Responsibility #2: validate number

DRY – Don’t repeat yourself

By Contract / Defensive

programming

programming

defensively means you’re making sure the

client gets “safe” response, no matter what the client wants to have happen

Programming by contract means you are working with a client code

to agree on how you’ll handle problem situations

Defensive programming