【C++】typeinfo.h

函数typeid()返回值类型class type_info。

其中type_info重载了操作符==, !=, =分别用来比较是否相等、不等、赋值。

函数name()返回类型名称。

class type_info {
public:
  virtual ~type_info();
  booloperator== (consttype_info& rhs) const;
  booloperator!= (consttype_info& rhs) const;
  boolbefore (consttype_info& rhs) const;
  constchar* name() const;
private:
  type_info (consttype_info& rhs);
  type_info& operator= (consttype_info& rhs);
};

当类型是类和类指针时需要注意：

正常类基类指针base*指向继承类deived，则typeid(deived) != typeid(*base) 前者类型是继承类的type_info类型，而后者是父类的type_info类型。

虚类基类指针base*指向继承类deived，则typeid(deived) == typeid(*base) 两者都是父类的type_info类型。

// type_info example
#include <iostream>
#include <typeinfo>
using namespace std;

struct Base {};
struct Derived : Base {};
struct Poly_Base {virtual void Member(){}};
struct Poly_Derived: Poly_Base {};

int main() {
    // built-in types:
    int i;
    int * pi;
    cout << "int is: " << typeid(int).name() << endl;
    cout << "  i is: " << typeid(i).name() << endl;
    cout << " pi is: " << typeid(pi).name() << endl;
    cout << "*pi is: " << typeid(*pi).name() << endl << endl;

    // non-polymorphic types:
    Derived derived;
    Base* pbase = &derived;
    cout << "derived is: " << typeid(derived).name() << endl;
    cout << " *pbase is: " << typeid(*pbase).name() << endl;
    cout << boolalpha << "same type? "; 
    cout << ( typeid(derived)==typeid(*pbase) ) << endl << endl;

    // polymorphic types:
    Poly_Derived polyderived;
    Poly_Base* ppolybase = &polyderived;
    cout << "polyderived is: " << typeid(polyderived).name() << endl;
    cout << " *ppolybase is: " << typeid(*ppolybase).name() << endl;
    cout << boolalpha << "same type? "; 
    cout << ( typeid(polyderived)==typeid(*ppolybase) ) << endl << endl;
}