Typeid
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- The correct title of this article is typeid. The initial letter is shown capitalized due to technical restrictions.
In C++, the typeid keyword is used to determine the class of an object at runtime. According to the C++ specification, it returns a reference to type_info. typeid is often preferred to dynamic_cast<class_type> in situations where just the class information is needed, because typeid is a constant-time procedure, whereas dynamic_cast must traverse the class derivation lattice of its argument at runtime.
[edit] Example
#include <iostream>
#include <typeinfo>
using namespace std;
class Person {
public:
// ... Person members ...
virtual ~Person() {}
};
class Employee : public Person {
// ... Employee members ...
};
int main ()
{
Person person;
Employee employee;
Person *ptr = &employee;
cout << typeid(person).name() << endl;
cout << typeid(employee).name() << endl;
cout << typeid(ptr).name() << endl;
cout << typeid(*ptr).name() << endl;
return 0;
}
Output (exact output varies by system):
Person Employee *Person Employee
