最新ch11ObjectOrientedDesignUseCaseRealizations教学讲义ppt课件.ppt

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1、ch11ObjectOrientedDesignUseCaseRealizations1.OverviewTheusecaserealizationisusedtoextendtheprocessofdetaileddesign.Inusecaserealization,eachusecaseistakenindividuallytodeterminealltheclassesthatcollaborateonit.Aspartofthatprocess,anyotherutilityorsupportclasses

2、areidentified.Careistakenduringthisprocesstodefinetheclassessotheintegrityofthemultilayerarchitecturaldesignismaintained.Asthedetailsoftheclassesaredesigned—usecasebyusecase—thedesignclassdiagramisalsoupdatedasnecessary.2021/8/92.DetailedDesignofMultilayerSyste

3、msCRCcardsfocusoncollaboratingdomainobjectstoexecutevarioususecases.Inmultilayerarchitecture,therearethreeobjectsrepresentingthethreelayersofasystem.Eachobjecthascertainresponsibilities.Theinputwindowobjecthastheprimaryresponsibilityofformattingandpresentingstu

4、dentinformationonthescreen.Thestudentobjectrepresentsthemiddlelayer,orbusinesslogiclayer,fortheusecase.Thedatabaseaccessobjectrepresentsthethirdlayerinthemultilayerdesign.2021/8/9PatternspecificationPatternspecificationhasfivemainelements:PatternnameProblemthat

5、requiresasolutionSolutiontoorexplanationofthepatternExampleofthepatternBenefitsandconsequencesofthepattern2021/8/9Pattern:ControllerProblem:Domainclasseshavetheresponsibilityofprocessingusecases.However,sincetherecanbemanydomainclasses,whichone(s)shouldberespon

6、sibleforreceivingtheinputmessages?Userinterfaceclassesbecomeverycomplexiftheyhavevisibilitytoallofthedomainclasses.Howcanthecouplingbetweentheuser-interfaceclassesandthedomainclassesbereduced?2021/8/9Pattern:ControllerSolution:Assigntheresponsibilityforreceivin

7、ginputmessagestoaclassthatreceivesallinputmessagesandactsasaswitchboardtoforwardthemtothecorrectdomainclass.Thereareseveralwaystoimplementthissolution:Haveasingleclassthatrepresentstheentiresystem,orHaveaclassforeachusecaseorrelatedgroupofusecasestoactasausecas

8、ehandler.2021/8/9Pattern:ControllerExample:TheRMOCustomeraccountsubsystemacceptsinputsfroma:CustomerFormwindow.Theseinputmessagesarepassedtothe:CustomerHandler,whichactsasth