typeid操作符

typeid() operator返回type_info，返回值不可拷贝、不可赋值

// Illustrates the typeid operator.

#include <iostream>

#include <typeinfo>

using namespace std;

struct PolyBase { virtual ~PolyBase() {} };

struct PolyDer : PolyBase { PolyDer() {} };

struct NonPolyBase {};

struct NonPolyDer : NonPolyBase { NonPolyDer(int) {} };

int main() {

  // Test polymorphic Types

  const PolyDer pd;

  const PolyBase* ppb = &pd;

  cout << typeid(ppb).name() << endl;

  cout << typeid(*ppb).name() << endl;

  cout << boolalpha << (typeid(*ppb) == typeid(pd))

       << endl;

  cout << (typeid(PolyDer) == typeid(const PolyDer))

       << endl;

  // Test non-polymorphic Types

  const NonPolyDer npd(1);

  const NonPolyBase* nppb = &npd;

  cout << typeid(nppb).name() << endl;

  cout << typeid(*nppb).name() << endl;

  cout << (typeid(*nppb) == typeid(npd)) << endl;

  // Test a built-in type

  int i;

  cout << typeid(i).name() << endl;

  return 0;

} ///:~

输出结果是：

struct PolyBase const *

struct PolyDer

true

true

struct NonPolyBase const *

struct NonPolyBase

false

int

The first output line just echoes the static type of ppb because it is a pointer. To get RTTI to kick in, you need to look at the pointer or reference destination object, which is illustrated in the second line. Notice that RTTI ignores top-level const and
volatile qualifiers. With non-polymorphic types, you just get the static type (the type of the pointer itself). As you can see, built-in types are also supported.

巴特西

typeid操作符

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