嵌軟第二學(xué)期系統(tǒng)分析與設(shè)計chap

Discussion

Whatisyourperceptionofobjecttechnology?

Whatdoyouperceiveasobjecttechnology’sstrengths?Itsweaknesses?

Whyareyoumakingtheshifttoobjecttechnology?

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WhatIsObjectTechnology?

Asetofprinciples( ion,encapsulation,polymorphism)guidingsoftwareconstruction,togetherwithlanguages,databases,andothertoolsthatsupportthoseprinciples.

–(ObjectTechnology–AManager’sGuide,Taylor,1997.)

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TheStrengthsofObjectTechnology

Reflectsasingleparadigm

Facilitatesarchitecturalandcodereuse

Reflectsrealworldmodelsmoreclosely

Encouragesstability

Isadaptivetochange

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DifferencesBetweenOOandStructuredDesignObject-orientation(OO)

Meldsthedataanddataflowprocesstogetherearlyinthelifecycle

Hasahighlevelofencapsulation

Promotesreuseofcodedifferently

Permitsmoresoftwareextensibility

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AFormalDefinitionofObject

Anobjecthasstate

Stateisaconditionorsituationduringthelifeofanobject,whichsatisfiessomecondition,performssomeactivity,orwaitsforsomeevent.

Thestateofanobjectnormallychangesovertime.

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Anobjecthasbehavior

Behaviordetermineshowanobjectactsandreacts.

Thevisiblebehaviorofanobjectismodeledbyasetofmessagesitcanrespondto(operationsthattheobjectcanperform).

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對象可唯一識別

即使對象有相同的特性，還是能識別每個不同的對象

Professor“JClark”teachesBiology

Professor“JClark”teachesBiology

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BasicPrinciplesofObjectOrientation

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WhatIs ion?

Theessentialcharacteristicsofanentitythatdistinguishesitfromallotherkindsofentities.

Definesaboundaryrelativetothe oftheviewer.

Isnotaconcretemanifestation,denotestheidealessenceofsomething.

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抽象示例

學(xué)生 教授

課程提供(9:00AM,周一，

周三，周五) 課程(例如，代數(shù)學(xué))

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WhatIsEncapsulation?

Hidesimplementationfrom s.

sdependoninterface.

ImprovesResiliency

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封裝（Encapsulation）

對客戶隱藏實現(xiàn)

客戶依賴于接口

提高了彈性

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WhatIsModularity?

Breaksupsomethingcomplexintomanageablepieces.

Helpspeopleunderstandcomplexsystems.

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模塊化示例

系統(tǒng)

課程 系統(tǒng)

課程 系統(tǒng)

學(xué)生管理系統(tǒng)

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WhatIsHierarchy?

Review(1)

Whatisanobject?

Whatisanattribute?Anoperation?

Whatarethefourprinciplesofobjectorientation?Describeeach.

WhatIs ion?

WhatIsEncapsulation?

WhatIsModularity?

WhatIsHierarchy?

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RepresentingObjectsintheUML

繼承（Inheritance）

使用已存在的定義做為基礎(chǔ)建立新定義的技術(shù)

桌子

家具

床

衣柜

椅子

椅子的實例

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多態(tài)（Polymorphism）

對于相同的消息，讓各個對象產(chǎn)生不同的行為

銷售 事務(wù)

雖不知道對象員工是做什么工作的，但只要對員工發(fā)出指令就行了

技術(shù)

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多態(tài)性示例

計算各員工工資的程序

不用多態(tài)性時 使用多態(tài)性時

if(員工對象=“銷售”){

payment=計算銷售人員工資();

}elseif(員工對象=“技術(shù)”){

payment=計算技術(shù)人員工資();

}elseif(員工對象=“事務(wù)”){

payment=計算事務(wù)人員工資();

}

payment=員工對象.工資計算();

工作分工一增加，程序就必須修改

即使工作分工增加，程序也不需要修改

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Discussion

Whatisanactivitydiagramandwhywouldyouuseone?

Whatisthedifferencebetweenanactivityandanaction?

Whatisapartition?

Whatarethedifferenttypesofin ctiondiagrams?

Whatisacombinedfragment?

Whataresomeexamplesofin ctionoperators?

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Discussion

Whatisgeneralization?Whatinheritance?

Whatispackage?Whyusepackages?

Definepolymorphism.Provideanexampleofpolymorphism.

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Assignments

Group,4-5 seach,oneteamleader(PM)

Prepareasoftwaresystem,

whosescaleis