C++面向?qū)ο蟪绦蛟O(shè)計(jì)雙語教程（第3版）課件 ch03Foundation of Classes and Objects-Data Abstraction and Definition of Classes、ch04Advance of Classes and Objects-

FoundationofClassesandObjects—DataAbstractionandDefinitionofClassesC++面向?qū)ο蟪绦蛟O(shè)計(jì)雙語教程(第3版)Chapter301IntroductiontoStructuresAstructuretypeisauser-definedtype.Structuresareaggregatedatatypebuiltbyusingelementsofothertypes，thatis，structuresareawayofstoringmanydifferentvaluesinvariablesofpotentiallydifferenttypesunderthesamename.Thismakesitamoremodularprogram，whichiseasiertomodifybecauseitsdesignmakesthingsmorecompact.Forexample，astructurecanbeusedtostoreinformationaboutstudentsinadatabase.IntroductiontoStructuresWhenyoudefineastructure，youmustrememberthatthemaindifferencebetweenstructuresandarraysisthatthestruetureisacollectionofdifferentdatatypesandthearrayisacollectionofthesamedatatype.IntroductiontoStructuresDefiningaStructureinC++Theprecedingstructuredefinitiondoesnotreserveanyspaceinmemory，rather，thedefinitioncreatesanewdatatypethatisusedtodeclareavariable.Structure'svariableis

declaredlikevariablesofothertypes.IntroductiontoStructuresTheprogramdefinesasingleDatestructurecalledtodayandusesthedotoperatortoinitializethestructurememberswiththevalues18forday，11formonth，and2010foryear.Theprogramthenaddsanumbertomemberyearbycallingfunctionaddyear，andprintsthedateintheEnglishstandardformat.AccessingMembersofStructuresIntroductiontoStructuresStructureswithMemberFunctionsTheresultofthisprogramisthesameastheoneofExample3-1.However，thefunctionsdefinedinLines9，10and11areplacedinsidetheDatestruetureasmembers.Thesefunctionsareaccessedusingamemberaccessoperator()，asmentionedinLines18and21.IntroductiontoStructures02DataAbstractionandClassesDataAbstractionAsthedevelopedsoftware

becomes

more

complex，wedesignmethodsanddata

structuresinparallel.Weprogressfromthelogicalorabstractdatastructureenvisionedatthe

toplevelthroughtherefinementprocessuntilwereachtheconcretecoding.DataAbstractionandClassesChapter1introducedtheprogrammingmethodologycalledobject-orientedprogramming

（OOP）.InOOP，thefirststepistoidentifythecomponents（calledobjects）byusingtheprincipleofdataabstraction.Anobjectisthevariableofaclasswhichcombinesdataandtheoperationsonthatdatainasingleunit.TheaimoftheC++classconceptistoprovidetheprogrammerwithatoolforcreatingnewtypesthatcanbeusedasconvenientlyasthebuilt-intypes.DefiningClassesDataAbstractionandClassesAnobjeetdoesnotexistuntilaninstanceoftheclasshasbeencreated；theclassisjustadefinition.Whentheobjectisphysicallycreated，thespaceforthatobjectisallocatedinthememory.Itispossibletohavemultipleobjeetscreatedfromoneclass.DefiningObjectsDataAbstractionandClassesFigure3-1showsavisualimageoftheclassobjectstodayandtomorrow.DataAbstractionandClassesIn-ClassMemberFunctionDefinitionAmemberfunctiondefinedwithintheclassdefinitionratherthansimplydeclaredthereistakentobeaninlinememberfunction.Thatis，in-classdefinitionofmemberfunctionsisforsmall，frequently-usedfunctions.DataAbstractionandClassesFileStructureofanAbstractDataTypeAnabstractdatatype（ADT）consistsoftwoparts：aspecificationandanimplementation.Thespecificationdescribesthebehaviorofthedatatypewithoutrefcrencetoitsimplementation.Theimplementationcreatesanabstractionbarrierbyhidingtheconcretedatarepresentationaswellasthecodefor

theoperations.DataAbstractionandClasses03InformationHidingTheprevioussectiondefinedtheDateclasstoimplementthedataoperationsinaprogram.Wethenwroteaprogram（Date.cpp）thatusedtheDateclass.Infaet，wecombinedtheDateclasswiththefunctiondefinitionstoimplementtheoperationsandthemainfunetionsoastocompletetheprogram.Thatis，thespecificationandimplementationdetailsoftheDateclass

weredirectlyincorporatedintotheprogram.InformationHidingIfseveralprogrammersusethesameobjectinaprojectwithdirectaccesstotheinternalpartsoftheobject，thereisnoguaranteethateveryprogrammerwillusethesameobjectinexactlythesameway.Thus，wemusthidetheimplementationdetails.Theusershouldknow

onlywhattheobjectdoes，nothowitdoes.InformationHidingHidingtheimplementationdetailsfreestheuserfromhavingtofitthisextrapieceofcodeintheprogram.Also，byhidingthedetails，wecanensurethatanobjectwillbeusedinexactlythesamewaythroughouttheproject.Furthermore，onceanobjecthasbeenwritten，debugged，andtestedproperly，itbecomes（andremains）error-free.InformationHidingToimplementDateinaprogram，theusermustdeclareobjectsofclassDate，andknow

whatoperationsareallowedandwhattheoperationsdo.Todoso，theusermusthaveaccesstothespecificationdetails.Astheuserisnotconcernedwiththeimplementationdetails，wemustputthosedetailsinaseparatefile.InformationHiding04AccessControlAkeyfeatureofobject-orientedprogrammingisinformation（data）hiding.Thistermdoesnotrefertotheactivitiesofparticularlyparanoidprogrammers；ratheritmeansthatdataisconcealedwithinaclasssothatitcannotbeaccessedmistakenlybyfunctionsoutsidetheclass.AccessControlTheprimarymechanismforhidingdataistoputitinaclassandmakeitprivate.Privatedataorfunctionscanonlybeaccessedfromwithintheclass.Publiedataorfunctions，ontheotherhand，areaccessiblefromoutsidetheclass.AccessControlThedeclarationoftheDateclassintheprevioussectionprovidesasetoffunctionsformanipulatingadate.However，itdoesnotspecifythatthosefunctionsshouldbetheonlyonestodependdirectlyonDate'srepresentationandtheonlyonestoaccessdirectlytotheDateobjects.AccessControlThepublicspecifierseparatestheclassbodyintotwoparts.Thenamesinthefirstpartwiththeprivatekeyword，includingdatamembersday，monthandyear，canbeusedonlybymemberfunctions.Thesecondpartwiththepublickeyword，includingmemberfunctionsinit_date，add_yearandprint，eonstitutesthepublicinterfacetoobjectsoftheclass.AccessControl05ConstructorsTheuseofthefunction，suchasinit_date，toprovideinitializationforclassobjectsis

inelegant.Becauseitisnowherestatedthatanobjectmustbeinitialized，aprogrammermay

forgettodosoordosotwice（oftenwithequallydisastrousresults）.ConstructorsDefinitionofConstructorsAconstructorisrecognizedbyhavingthesame

name

astheclassitself.Itservesthe

purposeofinitializingobjects.ConstructorsToguaranteethatthemembersofaclassareinitialized，youuseconstructors.Therearetwotypesofconstructors:withparametersandwithoutparameters.Theconstructorwithoutparametersiscalledthedefaultconstructor.OverloadingConstructorsConstructorsConstructorswithDefaultParametersAconstructorcanalsohavedefaultparameters.Insuchclass，therulesfordeclaringformalparametersarethesameasthosefordeclaringdefaultparametersinafunction.Moreover，actualparameterstoaconstructorwithdefaultparametersarepassedaccordingtotherulesforfunctionswithdefaultparameters.Constructors06DestructorsDefinitionofDestructorsAconstructorinitializesanobjeet.Inotherwords，itcreatestheenvironmentinwhichthememberfunctionsoperate.Sometimes，creatingthatenvironmentinvolvesacquiringaresource，suchasafile，alock，orsomememory，thatmustbereleasedafteruse.Thus，someclassesneedafunctionthatisguaranteedtobeinvokedwhenanobjectisdestroyedina

mannersimilartothewayaconstruetorisguaranteedtobeinvokedwhenanobjectiscreated.DestructorsUMLDiagramforClassesTheUnifiedModellingLanguage（UML）isnowthemostwidelyusedgraphicalrepresentationschemeformodelingobject-orientedsystem.Ithasindeedunifiedthevariouspopularschemes.Thosewhodesignsystemsusethelanguage（intheformofthediagram）tomodeltheirsystem，aswedothroughoutthisbook.DestructorsTheOrderofConstructorandDestructorCallsConstructorsanddestructorarecalledautomaticallybythecompiler.Theorderinwhichthesefunctioncallsaremadedependsontheorderinwhichtheirexecutionentersandleavesthescopesinwhichobjectsareinstantiated.Generally，thedestructorcallsaremadeinthereverseorderofthecorrespondingconstructorcalls.Destructors07EncapsulationEncapsulationisoneofthefundamentalprinciplesofobject-orientedprogramming.Itisthegroupingofrelatedideasintooneunit，whichcanthereafterbereferredtobyasinglename.Theprocessiscombiningdataandfunctionsintoasingleunitcalledclass.EncapsulationEncapsulationmeansthatalloftheobject'sdataiscontainedandhiddenintheobjectandsuchdataaccessisrestrictedtothemembersofthatclass，thatis，theprogrammercannotdirectlyaccessthedata.Dataisonlyaccessiblethroughthefunctionsexistinginsidetheclass.EncapsulationTheCounterclassinerementsanumberbyonesuccessivelyandreturnsthesum.ThepublicmemberfunctionsaddandgetSumaretheinterfacestotheoutsideworldandauserneedstoknowthemtousetheclass.Theprivatemembersumissomethingthatishiddenfrom

theoutsideworldbutisneededforproperclassoperation.EncapsulationInaword，Dataencapsulationleadstotheimportantconceptofdatahiding.Datahidingistheimplementationdetailsofaclassthatarehiddenfromtheuser.Encapsulation08CaseStudy:AGradeBookClassAccordingtothestatementsabove，theUMLdiagramoftheGradeBookclassisshowninFigure3-4.CaseStudy:AGradeBookClassFirst，wedeclarethreeprivatedatamemberscourseName，courseTeacherandcourseHourintheGradeBook.Thesedatamembersrepresenttheattributesoftheclass.Then，threesetmemberfunctionsaredeclaredtoresettheattributevalues，andthreegetfunetionsareusedto

obtaintheattributevalues.Finally，adisplayCourseMSGfunctionisdeclared.CaseStudy:AGradeBookClassIntheGradeBook.cppfile，wepresentthedefinitionsofmemberfunctionsoutsidetheclass.Totestthisclass，wecreatetwoobjectsoftheclass，namelygradeBooklandgradeBook2，inthemainfunetion.ThetwoobjectsaccessthedisplayCourseMSGmemberfunetiontodisplaytheinformationofthesetwocoursesrespectively.CaseStudy:AGradeBookClass謝謝觀看C++面向?qū)ο蟪绦蛟O(shè)計(jì)雙語教程(第3版)AdvanceofClassesandObjects—FurtherDefinitionofClassMembersandObjectsC++面向?qū)ο蟪绦蛟O(shè)計(jì)雙語教程(第3版)Chapter401ConstantMemberFunctionsandConstantObjectsTheDateclassdefinedsofarprovidesmemberfunctionsinordertogiveaDateobjectvaluesandchangeit.Unfortunately，wedidnotprovideawayofexaminingthevalueofaDate.Thisproblemcaneasilyberemediedbyaddingfunctionsforreadingtheday,month,andyear.ConstantMemberFunctionsandConstantObjectsNoteTheconstkeywordisplacedafterthe（empty）parameterlistinthefunctiondeclarations.It

indicatesthatthesefunctionseannotmodifythedatacontentofaDateclass.const關(guān)鍵字放置在函數(shù)聲明中的（空）參數(shù)列表之后，它表示這些函數(shù)不能修改Date類的數(shù)據(jù)內(nèi)容。ConstantMemberFunctionsandConstantObjectsSomeobjectsneedtobemodifiableandsomenot.Theconstkeywordcanbeusedtospecifythatanobjectisnotmodifiableandthatanyattempttomodifytheobjectshouldresultinacompilationerror.Aconstmemberfunctioncanbeinvokedforbothconstandnon-constobjects，whereasanon-constmemberfunctioncanbeinvokedonlyfornon-constobjects.ConstantMemberFunctionsandConstantObjects02thisPointersAnyobjecthasaccesstoitsownaddressthroughapointercalledthis.Butthethispointer

ofanobjectisnotpartoftheobjectsitself-i.e.thesizeofthememorytakenbythethispointerdoesnotaffecttheresultofasizeofoperationontheobjects.Forexample，boththesizesofthetodayandtomorrowobjeetsare12inthisexample.thisPointersWhenanon-staticmemberfunctioniscalledforanobjeet，thethispointerispassedasanimplicitargumenttoeachofthenon-staticmemberfunctionsofaclass，struct，oruniontype.However，staticmemberfunctionsdonothaveathispointer.thisPointersTheobject'saddressisavailablewithinthememberfunctionasthethispointer.Mostusagesofthisareimplicit.Itislegal，thoughunnecessary，toexplicitlyusethiswhenreferringtomembersoftheclass.thisPointersThethispointerisnotanordinaryvariable.Becausethethispointerisnon-modifiable，assignmentsto

this

are

not

allowed.this指針不是普通的變量。因?yàn)閠his指針是不可修改的，所以不允許給this指針賦值。thisPointers03StaticMembersInsideaclassdefinition，theclassmemberscanbedeclaredusingthestorageclassspecifierstatieintheclassmemberlist.Staticmembersofaclassarenotassociatedwiththeobjectsoftheclass：theyareindependentvariableswithstaticstorageduration.StaticMembersAstaticmemberisavariablethatispartofaclass，yetisnotpartofanobjectofthatclass.Onlyone

copyofthestaticmemberissharedbyallobjectsofaclassinaprogram.靜態(tài)成員是一個(gè)類的部分的變量，但不是該類對象的一部分。程序中一個(gè)類的所有對象只共享靜態(tài)成員的一個(gè)副本。StaticMembersAtypicaluseofstaticmembersisforrecordingdatacommontoallobjectsofaclass.Forexample，youcanuseastaticdatamemberasacountertostorethenumberofobjectsofaparticularclasstypethatarecreated.Eachtimeanewobjectiscreated，thisstaticdatamember

canbeincrementedtokeeptrackofthetotalnumberofobjects.StaticMembersWhenweinstantiateaclassobject，eachobjectgetsitsowncopyofallnormaldatamembers.Inthiscase，sincewehavedeclaredthreestudentclassobjects，weendupwiththreecopiesofcountoneinsidestl，thesecondinsidest2，andthethirdinsidest3.Theyshouldhavedifferentvaluesbecausethecountvariableisusedtokeeptrackofthetotalnumberof

objects.However，theygetthesamevalue0.StaticMembers04FreeStoreThefreestoreisapoolofmemoryavailableforyoutoalloeate（anddeallocate）storageforobjectsduringtheexecutionofyourprogram.Thenewanddeleteoperatorsareusedtoallocateanddeallocatefreestore，respectively.FreeStoreWhenyouaredonewithyourareaofmemory，youmustcallthedeletestatementonthepointer.Thedeletestatementreturnsthememorytothefreestore.Rememberthatthepointeritselfasopposedtothememorytowhichitpoints--isalocalvariable.Whenthefunctionin

whichitisdeclaredreturns，thatpointergoesoutofscopeandislost.FreeStoreThememoryallocated

byusingnewisnotfreedautomatically，however.Thatmemorybecomesunavailablea

situationcalledamemoryleak.Thenameisgiventodeseribethatthepartofmemorycannotberecovereduntiltheprogramends.Itisasthoughthememoryhasleakedoutofyourcomputer.FreeStoreJustasyoucancreateapointertoaninteger，youcancreateapointertoanyobject.IfyouhavedeclaredanobjectofclassDate，youcandeclareapointertothatclassandinstantiateaDateobjectonthefreestore，justasyoucanmakeoneonthestack.FreeStore05ObjectMembersDefinitionofObjectMembersSometimes，aclasshasadatamemberwhichisnotasimplebuilt-indatatypebutanaggregatebuilt-indata.Suchdatamemberisdefinedasanotherclassobject.Whenaclasshasobjectsofotherclassesasmembers，suchcapabilityiscalledcomposition.Compositionisaspecialcaseoftheaggregationrelationship.ObjectMembersForcreatingobjects，themembers

constructorsareinvokedbeforethebodyofthecontainingclass'ownconstructorisexecuted.Theconstructorsareinvokedintheorderinwhichthemembersaredeclaredintheclassratherthantheorderinwhichthemembersappear

intheinitializationlist.TheOrderofConstructorsandDestructorsforMemberObjectsObjectMembers為了確保成員對象的初始化要求，必須滿足下列條件之一：包含對象的類不需要構(gòu)造函數(shù)。包含對象的類有一個(gè)可訪問的默認(rèn)構(gòu)造函數(shù)。包含類的構(gòu)造函數(shù)都顯式地初始化包含的對象。ObjectMembersClassMembersbyUsingInitializersMemberinitializersareessentialfortypesforwhichinitializationdiffersfromtheassignment，thatis，formemberobjectsofclasseswithoutadefaultconstructor，forconstmembers，andforreferencemembers.ObjectMembers06CopyMembersThecopyconstructortakesareferencetoaconstparameter.Itisaconsttoguaranteethatthecopyconstructordoesnotchangeit.Inaddition，itisareferencebecauseavalueparameterwouldrequiremakingacopy，whichwouldinvokethecopyconstructor，thereforemakinga

copyofitsparameter.CopyMembersDefinitionofCopyConstructorsTheaboveisanexampleofacopyconstructorfortheDateclass，whichdoesnotreallyneedonebecausethedefaultcopyconstructor'sactionofcopyingdatawouldworkfine.Still，itshowshowitworks.CopyMembersDefinitionofCopyConstructorsShallowCopyAshallowcopymeansthatC++copieseachmemberoftheclassindividuallyusingtheassignmentoperator（=）.Whenclassesaresimple

e.g.donotcontainanydynamically

allocatedmemory），thisworksverywellliketheexampleabove.CopyMembersDeepCopyTherootofthisproblemistheshallowcopydonebythecopyconstructordoingashallowcopyonpointervaluesinaeopyconstructororanoverloadedassignmentoperator（=）usuallymeanstrouble.Thesolutiontothisproblemistodoadeepcopyonanynon-null

pointersbeingcopied.CopyMembers07ArraysofObjectsInitializeanObjectArraybyUsingaDefaultConstructorSupposethatyoudeclareanarrayof4classobjects，forexample，4Dateobjects.youneedtodisplaytheirdays，monthsandyears.YouhavetodeclareonearrayarrayDateof4elementseach，whereineachelementisanobjectoftypeDate.ArraysofObjectsInitializeanObjectArraybyUsingaDefaultConstructorInthisease，itisimpracticaltospecifydifferentconstructorsforeachelement.Therefore，thedefaultconstructorisusedtoin