C++中关于判断一个类是否继承于另外一个类的方法？该如何处理

C++中关于判断一个类是否继承于另外一个类的方法？
Class A
{
Public:
Virtual void function(){}
}

Class B:public class A
{
Public:
Virtual void function(){}
}

Class C:public class B
{
Public:
Virtual void function(){}
}

C* p=new C;
我现在运行时刻判断C类是否继承于B或则A，应该怎么在C++中实现？比如说，我有下面这个函数
IsDerivedFrom(C,A)，这样的功能应该怎么实现？


[解决办法]

C/C++ code

#include<iostream>using namespace std;class A { public: virtual void function(){} } ;class B:public  A { public: virtual void function(){} } ;class C:public  A { public: virtual void function(){} } ;void   main() {     C* p=new C;    try    {        B* s = dynamic_cast<B*>(p);        cout <<"OK"<<endl;    }    catch(...)    {        cout<<"NOT OK"<<endl;    }}
[解决办法]
Loki库里有方法的，google: Loki, c++。参考一本书，中文名叫《编程新思维，C++范型编程与设计模式》，是Loki的作者的论文集。不过这样的技巧属于范型编程，很难理解。运行中可以用dynamic_cast,例如：

A* a;
....

if (C* cp=dynamic_cast<C*>(a))
{
    //it is sure that C is derived from A, or C & A are the same type
}

[解决办法]
struct Small { char c; };
struct Big { small s[2]; };

Small ISA(...);
Big ISA(A*);

template <class C, class A>
struct IsDrivedFrom
{
 enum { RET = (sizeof(ISA(new C)) == sizeof(Big)) );
}

[解决办法]
#include <iostream>
using namespace std;

template <int n>
struct Tag { Tag<n-1> x[2]; };

template <>
struct Tag<0> { char c; };

#define CheckMember(RES,TC,VN,VT)\
struct RES\
{\
   struct Flag {};\
   static Flag* VN;\
\
   struct HasMemberHelper : public TC\
   {\
       Tag<0> check(Flag*);\
       Tag<1> check(...);\
       Tag<2> check(VT &);\
       int helper()\
       {\
           return sizeof(check(VN));\
       }\
       static int Result()\
       {\
           HasMemberHelper f;\
           return f.helper();\
       }\
   };\
   static int result() { return HasMemberHelper::Result(); }\
};

void explain_result(int r)
{
   if(r == sizeof(Tag<0>))
   {
       cout << "Test class has no member named foo.";
   }
   else if(r == sizeof(Tag<1>))
   {
       cout << "Test class has member named foo but type is mismatch.";
   }
   else if(r == sizeof(Tag<2>))
   {
       cout << "Test class has member named foo and type is match also.";
   }
   cout << endl;
}


//-----------------------------------------------
//  定义三个测试类
struct TestA
{
int foo;
};

struct TestB
{
   char foo;
};

struct TestC
{
   int woo;
};

//-----------------------------------------------
//  检查给定的测试类是否含有名为foo的成员变量.
//  并且类型是否为int
CheckMember(DoesTestAHasMemberFoo, TestA, foo, int);
CheckMember(DoesTestBHasMemberFoo, TestB, foo, int);
CheckMember(DoesTestCHasMemberFoo, TestC, foo, int);


int main()
{
   int r;

   cout << "Check TestA:" << endl;
   r = DoesTestAHasMemberFoo::result();
   explain_result(r);

   cout << "Check TestB:" << endl;
   r = DoesTestBHasMemberFoo::result();
   explain_result(r);

   cout << "Check TestC:" << endl; 
 
   r = DoesTestCHasMemberFoo::result();
   explain_result(r);

   return 0;
}