C中的运行时类型检查（RuntimetypecheckinC）

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1、C卄中的运行时类型检查(RuntimetypecheckinC++)RuntimetypecheckinC++2009/09/2310:20,A.M.synopsisOftenpeopleask,〃howcanIdetermineorcheckthetypeofobjectinC++atruntime?"Thefollowingisademonstrationofasimpleproblem.Thefollowingprogramdisplays，zBark，zonthefirstcallofCFoo::z/AnimalSayszand〃Miaou〃onthesecondcall/z.Cl

2、assAnimal*/}{/*••;ClassDog:publicAnimal{/**/}・・；ClassCat:publicAnimalClassCFooPublic:VoidAnimalSays(Anima1*){/**/}・・・}；Intmain(int,argc,char*,argv[])Dogrex;Catkitty;CFoofoo;Foo.AnimalSays(&rex);Foo.AnimalSays(&kitty);Return0;Thatis,youneedtodosomesortofmethodatruntimetodeterminethefunctionCFoo::the

3、argumentthatAnimalSaysaccepts,thepointertotheDogtypeobject,orthepointertotheCattypeobject・FirsttryOurfirstideawastoaddamembervariablethatstorestherelevantinformationaboutthetype・ttincludePublic:Enum,AnimalType,{TypeDog,TypeCat};};ClassDog:publicAnimal{Public:(Dog):m_type(TypeDog){}ConstAn

4、imalTypem_type;};ClassCat:publicAnimal{Public:(Cat):m_type(TypeCat){}}；ClassCFooPublic:VoidAnimalSays(Anima1*);};Intmain(int,argc,char*,argv[]){Dogrex;Catkitty;CFoofoo;Foo.AnimalSays(&rex);Foo.AnimalSays(&kitty);Return0;VoidCFoo::AnimalSays(Animal*,pAnimal)If(((Dog*)pAnimal)->m_type二Animal::TypeDog

5、)Std::cout,，，Bark，/!z/:Elseif(((Cat*)pAnimal)->m_type二Animal::TypeCat)Std::cout,“Miaou”！〃;Now,lookingbackattheimplementationpartofCFoo::AnimalSays,imagineifwedon，thaveonlytwoanimaltypes,butmorethan50(ie,derivedclassesfromAnimal)?Asaresult,notonlyisthecodeveryugly,it'shardtomakesureit'snotwrong,it's

6、alsohardtoread,modify,andmaintain・That'snotagoodsolution.AnothergoodwaytodoitSavesclassnamesinstaticmembervariablesandaccessesthemthroughvirtualfunctions・ttincludettincludePublic:string&);string&);VirtualboolIsOfType(conststd::string&)二0;}；ClassDog:publicAnimal{Staticconststringm_

7、class_name;Public:VirtualboolIsOfType(conststd::};ClassCat:publicAnimal{Staticconststringm_class_name;Public:VirtualboolIsOfType(conststd::}；ClassCFooPublic:VoidAnimalSays(Anima1*);};Intmain(int,argc,char*,