std::is_object (3) - Linux Manuals

std::is_object: std::is_object

NAME

std::is_object - std::is_object

Synopsis

Defined in header <type_traits>
template< class T > (since C++11)
struct is_object;

If T is an object_type (that is any possibly cv-qualified type other than function, reference, or void types), provides the member constant value equal true. For any other type, value is false.

Template parameters

T - a type to check

Helper variable template

template< class T > (since C++17)
inline constexpr bool is_object_v = is_object<T>::value;

Inherited from std::integral_constant

Member constants

value true if T is an object type , false otherwise
         (public static member constant)
[static]

Member functions

              converts the object to bool, returns value
operator bool (public member function)

operator() returns value
              (public member function)
(C++14)

Member types

Type Definition
value_type bool
type std::integral_constant<bool, value>

Possible implementation

  template< class T>
  struct is_object : std::integral_constant<bool,
                       std::is_scalar<T>::value ||
                       std::is_array<T>::value ||
                       std::is_union<T>::value ||
                       std::is_class<T>::value> {};

Example

// Run this code

  #include <iostream>
  #include <type_traits>

  int main() {
      class cls {};
      std::cout << std::boolalpha;
      std::cout << std::is_object<int>::value << '\n';
      std::cout << std::is_object<int&>::value << '\n';
      std::cout << std::is_object<cls>::value << '\n';
      std::cout << std::is_object<cls&>::value << '\n';
  }

Output:

  true
  false
  true
  false