dynamic_cast的有效性问题

来源：互联网发布：excel统计多列数据编辑：程序博客网时间：2024/04/30 05:50

/********************************************************************  file name : CLK.h  author  :   Clark/陈泽丹  created :   2011-12-12  purpose :   测试dynamic_cast的转换有效性 测试结果发现dynamic_cast的只能在 [根结点, 实例化对象所处的类] 的路径上才能成功转换*********************************************************************/ #include <iostream>using namespace std;#define DECLARE_CLASS_CREATE(class_name) static char* getName() { return #class_name; }; template<class T_TYPE>class T2T{public:typedef T_TYPE CUR_TYPE;};class Root{public:DECLARE_CLASS_CREATE(Root)virtual void show(){} };class Root_1Ex:public Root{public:DECLARE_CLASS_CREATE(Root_1Ex)};class Root_1Ex_1Ex:public Root_1Ex{public:DECLARE_CLASS_CREATE(Root_1Ex_1Ex)};class Root_2Ex:public Root{public:DECLARE_CLASS_CREATE(Root_2Ex)};template<class T_Base, class T_Ex, class T_Test>void Test_Dynamic_Cast(T_Base obj1, T_Ex obj2, T_Test obj3){cout<<"-----------------------------------------------------------"<<endl;T_Base::CUR_TYPE* pBase = new T_Ex::CUR_TYPE();if( NULL != pBase){cout<<"Succeed: "<<T_Base::CUR_TYPE::getName()<<" = new "<< T_Ex::CUR_TYPE::getName()<<endl;}else{cout<<"Failed: "<<T_Base::CUR_TYPE::getName()<<" = new "<< T_Ex::CUR_TYPE::getName()<<endl;}T_Test::CUR_TYPE* pTest = dynamic_cast<T_Test::CUR_TYPE*>(pBase);if( NULL != pTest){cout<<"Succeed: "<<"dynamic_cast<"<< T_Test::CUR_TYPE::getName()<<"*>("<<T_Base::CUR_TYPE::getName()<<")"<<endl;}else{cout<<"Failed: "<<"dynamic_cast<"<< T_Test::CUR_TYPE::getName()<<"*>("<<T_Base::CUR_TYPE::getName()<<")"<<endl;}cout<<"-----------------------------------------------------------"<<endl;cout<<endl;}void main(){Test_Dynamic_Cast(T2T<Root>(), T2T<Root_1Ex>(), T2T<Root_1Ex>());Test_Dynamic_Cast(T2T<Root>(), T2T<Root_1Ex>(), T2T<Root_1Ex_1Ex>());Test_Dynamic_Cast(T2T<Root>(), T2T<Root_1Ex>(), T2T<Root_2Ex>());Test_Dynamic_Cast(T2T<Root>(), T2T<Root_1Ex_1Ex>(), T2T<Root_1Ex>());system("pause");}

运行结果:

-----------------------------------------------------------
Succeed: Root = new Root_1Ex
Succeed: dynamic_cast<Root_1Ex*>(Root)
-----------------------------------------------------------

-----------------------------------------------------------
Succeed: Root = new Root_1Ex
Failed: dynamic_cast<Root_1Ex_1Ex*>(Root)
-----------------------------------------------------------

-----------------------------------------------------------
Succeed: Root = new Root_1Ex
Failed: dynamic_cast<Root_2Ex*>(Root)
-----------------------------------------------------------

-----------------------------------------------------------
Succeed: Root = new Root_1Ex_1Ex
Succeed: dynamic_cast<Root_1Ex*>(Root)
-----------------------------------------------------------