std::is_object

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

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.

The behavior of a program that adds specializations for is_object or is_object_v (since C++17) is undefined.

Template parameters

T - a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants

value
[static]
 true if T is an object type , 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>

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

#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

See also

(C++11)
 checks if a type is a scalar type
(class template)
(C++11)
 checks if a type is an array type
(class template)
(C++11)
 checks if a type is an union type
(class template)
(C++11)
 checks if a type is a non-union class type
(class template)