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;
}