C++編程思想答案第十四章其他章節(jié)點擊用戶名找thinkinginC++annotatedsolutionguide(charpter14)C++編程思想答案第十四章其他章節(jié)點擊用戶名找thinkinginC++annotatedsolutionguide(charpter14)C++編程思想答案第十四章其他章節(jié)點擊用戶名找thinkinginC++annotatedsolutionguide(charpter14)C++編程思想答案第十四章其他章節(jié)點擊用戶名找thinkinginC++annotatedsolutionguide(charpter14)編制僅供參考審核批準生效日期地址：電話：傳真:郵編:[ViewingHints][BookHomePage][FreeNewsletter]

[Seminars][SeminarsonCDROM][Consulting]AnnotatedSolutionGuideRevisionforThinkinginC++,2ndedition,Volume1byChuckAllison?2001MindView,Inc.AllRightsReserved.[PreviousChapter][TableofContents][NextChapter]Chapter1414-1ModifysothatitalsoinheritsfromaclasscalledVehicle,placingappropriatememberfunctionsinVehicle(thatis,makeupsomememberfunctions).AddanondefaultconstructortoVehicle,whichyoumustcallinsideCar’sconstructor.14-2Createtwoclasses,AandB,withdefaultconstructorsthatannouncethemselves.InheritanewclasscalledCfromA,andcreateamemberobjectofBinC,butdonotcreateaconstructorforC.CreateanobjectofclassCandobservetheresults.14-3Createtwoclasses,AandB,withdefaultconstructorsthatannouncethemselves.InheritanewclasscalledCfromA,andcreateamemberobjectofBinC,butdonotcreateaconstructorforC.CreateanobjectofclassCandobservetheresults.Solution:14-4Createathree-levelhierarchyofclasseswithdefaultconstructors,alongwithdestructors,bothofwhichannouncethemselvestocout.Verifythatforanobjectofthemostderivedtype,allthreeconstructorsanddestructorsareautomaticallycalled.Explaintheorderinwhichthecallsaremade.Solution:Applyingthisprinciplerecursivelyrequiresthatthesub-objectatthetopofthehierarchymustbecreatedfirst.Destructionisalwaysthereverseorderofconstruction.(Exercises14-5through14-8arelefttothereader.)14-5In,createaclassDthatinheritsfromBandhasamemberobjectofclassC.Addcodetoshowwhentheconstructorsanddestructorsarebeingcalled.14-6ModifytoaddanotherlevelofinheritanceDerived3withmemberobjectsofclassMember4andMember5.Tracetheoutputoftheprogram.14-7In,verifythatinDerived2,Derived3,andDerived4,noneofthebase-classversionsoff()areavailable.14-8Modifybyaddingthreeoverloadedfunctionsnamedh()toBase,andshowthatredefiningoneoftheminaderivedclasshidestheothers.14-9InheritaclassStringVectorfromvector<void*>andredefinethepush_back()andoperator[]memberfunctionstoacceptandproducestring*.Whathappensifyoutrytopush_back()avoid*

Solution:ThismakesStringVectortype-safe.NotethatIoverloadedbothversionsofoperator[](constandnon-const).Ifyou’vedoneanyamountofreadingonobject-orientedprogramminginC++,youprobablyhavelearnedthatyoushouldneveroverrideanon-virtualfunctionfromapublicly-inheritedclass(seeforexample,ScottMeyers“EffectiveC++”,Item37).Thestandardcontainerssuchasvectorhavenovirtualfunctionsatall,sotheremustbeabetterwaytodefineStringVector.TheBetterWayistouseprivateinheritance,andprovideaccesstotheinheritedfunctionsasthefollowingversionillustrates.classStringVector:privatevector<void*>{public:voidpush_back(string*s){vector<void*>::push_back(s);}string*&operator[](size_tn){returnreinterpret_cast<string*>(vector<void*>::operator[](n));}conststring*operator[](size_tn)const{returnreinterpret_cast<conststring*>(vector<void*>::operator[](n));}usingvector<void*>::size;};Privateinheritancecombinedwithtemplatesmakesbuildingsuchtype-safecontainersfairlysimple.(SeeChapter16andVolume2).(Exercises14-10through14-13arelefttothereader.)14-10Writeaclasscontainingalongandusethepsuedo-constructorcallsyntaxintheconstructortoinitializethelong.14-11CreateaclasscalledAsteroid.UseinheritancetospecializethePStashclassinChapter13&sothatitacceptsandreturnsAsteroidpointers.Alsomodifytotestyourclasses.ChangetheclasssoPStashisamemberobject.14-12RepeatExercise11withavectorinsteadofaPStash.14-13In,modifyChesstogiveitadefaultconstructor,copy-constructor,andassignmentoperator.Demonstratethatyou’vewrittenthesecorrectly.14-14CreatetwoclassescalledTravelerandPagerwithoutdefaultconstructors,butwithconstructorsthattakeanargumentoftypestring,whichtheysimplycopytoaninternalstringvariable.Foreachclass,writethecorrectcopy-constructorandassignmentoperator.NowinheritaclassBusinessTravelerfromTravelerandgiveitamemberobjectoftypePager.Writethecorrectdefaultconstructor,aconstructorthattakesastringargument,acopy-constructor,andanassignmentoperator.Solution:Thekeypointofthisexerciseistogettheconstructorandassignmentoperatorcorrectwithinheritance.Bothneedtomakesurethatthebaseclasssub-objectistakencareof(whichissometimeseasytoforget!).Inconstructorsyouusetheinitializerlist;inassignmentoperatorsyouexplicitlycallthebaseclassassignmentoperator(sincethebaseclassdataisprivate,youhavenochoice).14-15Createaclasswithtwostaticmemberfunctions.Inheritfromthisclassandredefineoneofthememberfunctions.Showthattheotherishiddeninthederivedclass.Solution:14-16Lookupmoreofthememberfunctionsforifstream.In,trythemoutonthefileobject.(Lefttothereader)14-17Useprivateandprotectedinheritancetocreatetwonewclassesfromabaseclass.Thenattempttoupcastobjectsofthederivedclasstothebaseclass.Explainwhathappens.Solution:Thesetypesofinheritanceareusedforimplementationonly,therefore,clientsthatonlyhavethepublicinterfaceavailablehavenosuchaccess.14-18In,addamemberfunctioninDerivedthatcallstheprotectedBasememberread().(Lefttothereader.)14-19ChangesothatDerivedisusingprotectedinheritance.Seeifyoucancallvalue()foraDerivedobject.(Lefttothereader.)14-20CreateaclasscalledSpaceShipwithafly()method.InheritShuttlefromSpaceShipandaddaland()method.CreateanewShuttle,upcastbypointerorreferencetoaSpaceShip,andtrytocalltheland()method.Explaintheresults.Solution:ThevariableshipisaSpaceShip,whichdoesnothavealand()method.IfSpaceShiphadalandmethod,therewouldstillbeaproblem:SpaceShip::land()wouldbecalledinsteadofShuttle::land()(rarelytherightthingtodo!).Thismysteryissolvedinthenextchapter(readaboutvirtualfunctions).(Exercises14-21through14-25arelefttothereader.)14-21Modifytoaddaprepare()methodtoInstrument.Callprepare()insidetune().14-22Modifysothatplay()printsamessagetocout,andWindredefinesplay()toprintadifferentmessagetocout.Runtheprogramandexplainwhyyouprobablywouldn’twantthisbehavior.Nowputthevirtualkeyword(whichyouwilllearnaboutinChapter15)infrontoftheplay()declarationinInstrumentandobservethechangeinthebehavior.14-23In,inheritanewclassfromChildandgiveitaMemberm.Writeaproperconstructor,copy-constructor,operator=,andoperator<<forostreams,andtesttheclassinmain().14-24Taketheexampleandmodifyitbyaddingyourowncopy-constructortoChildwithoutcallingthebase-classcopy-constructorandseewhathappens.Fixtheproblembymakingaproperexplicitcalltothebase-classcopyconstructorintheconstructor-initializerlistoftheChildcopy-constructor.14-25Modifytouseavector<string>insteadofaStack.14-26CreateaclassRockwithadefaultconstructor,acopy-constructor,anassignmentoperator,andadestructor,allofwhichannouncetocoutthatthey’vebeencalled.Inmain(),createavector<Rock>(thatis,holdRockobjectsbyvalue)andaddsomeRocks.Runtheprogramandexplaintheoutputyouget.NotewhetherthedestructorsarecalledfortheRockobjectsinthevector.Nowrepeattheexercisewithavector<Rock*>.Isitpossibletocreateavector<Rock&>

Solution:EvenbyPtrstorescopies;they’rejustcopiesofthepointersyousenttopush_back().Asyoucanalsosee,thedestructorofbyValueensuresthatallitselements(copies)aredestroyed.(Again,sodoesbyPtr;pointersjustdon’thavedestructors,soyouseenotraceoutput).Itmakesnosensetohaveavectorofreferences,sincevectorsstorecopies.Ifyoustoreheappointersinacontainer,youareresponsibletodeletethem.14-27Thisexercisecreatesthedesignpatterncalledproxy.StartwithabaseclassSubjectandgiveitthreefunctions:f(),g(),andh().NowinheritaclassProxyandtwoclassesImplementation1andImplementation2fromSubject.ProxyshouldcontainapointertoaSubject,andallthememberfunctionsforProxyshouldjustturnaroundandmakethesamecallsthroughtheSubjectpointer.TheProxyconstructortakesapointertoaSubjectthatisinstalledintheProxy(usuallybytheconstructor).Inmain(),createtwodifferentProxyobjectsthatusethetwodifferentimplementations.NowmodifyProxysothatyoucandynamicallychangeimplementations.Solution:Thisisthewell-knownProxypatternfromtheGangofFour(see"DesignPatterns",Gammaetal,Prentice-Hal