typeid参数

最新推荐文章于 2021-10-26 15:32:14 发布

Yerasel

最新推荐文章于 2021-10-26 15:32:14 发布

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分类专栏： C++ 文章标签： class object delete

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本文通过C++示例代码展示了如何使用typeid运算符获取对象的实际类型信息，特别关注指向派生类的基类指针所指向的对象类型。讨论了不同类型指针及引用在typeid运算符作用下的行为差异。

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http://msdn.microsoft.com/en-us/library/fyf39xec(v=VS.80).aspx

If the expression points to a base class type, yet the object is actually of a type derived from that base class, a type_info reference for the derived class is the result. The expression must point to a polymorphic type (a class with virtual functions). Otherwise, the result is the type_info for the static class referred to in the expression. Further, the pointer must be dereferenced so that the object it points to is used. Without dereferencing the pointer, the result will be the type_info for the pointer, not what it points to. For example:

// expre_typeid_Operator.cpp
// compile with: /GR /EHsc
#include <iostream>
#include <typeinfo.h>

class Base {
public:
   virtual void vvfunc() {}
};

class Derived : public Base {};

using namespace std;
int main() {
   Derived* pd = new Derived;
   Base* pb = pd;
   cout << typeid( pb ).name() << endl;   //prints "class Base *"
   cout << typeid( *pb ).name() << endl;   //prints "class Derived"
   cout << typeid( pd ).name() << endl;   //prints "class Derived *"
   cout << typeid( *pd ).name() << endl;   //prints "class Derived"
   delete pd;
}