std::is_class
From cppreference.com
| Defined in header <type_traits>
|
||
| template< class T > struct is_class; |
(since C++11) | |
Checks whether T is a class type. Provides the member constant value which is equal to true, if T is a class type (but not union). Otherwise, value is equal to false.
Contents |
[edit] Template parameters
| T | - | a type to check |
[edit] Helper variable template
| template< class T > inline constexpr bool is_class_v = is_class<T>::value; |
(since C++17) | |
Inherited from std::integral_constant
Member constants
| value [static] |
true if T is a class or struct , false otherwise (public static member constant) |
Member functions
| operator bool |
converts the object to bool, returns value (public member function) |
| operator() (C++14) |
returns value (public member function) |
Member types
| Type | Definition |
value_type
|
bool
|
type
|
std::integral_constant<bool, value> |
[edit] Possible implementation
namespace detail { template <class T> char test(int T::*); struct two { char c[2]; }; template <class T> two test(...); } template <class T> struct is_class : std::integral_constant<bool, sizeof(detail::test<T>(0))==1 && !std::is_union<T>::value> {}; |
[edit] Example
Run this code
#include <iostream> #include <type_traits> struct A {}; class B {}; enum class C {}; int main() { std::cout << std::boolalpha; std::cout << std::is_class<A>::value << '\n'; std::cout << std::is_class<B>::value << '\n'; std::cout << std::is_class<C>::value << '\n'; std::cout << std::is_class<int>::value << '\n'; }
Output:
true true false false
[edit] See also
| (C++11) |
checks if a type is an union type (class template) |
