< cpp‎ | types
Metaprogramming library
Type traits
Type categories
Type properties
(C++11)(until C++20)
(C++11)(deprecated in C++20)
Type trait constants
Supported operations
Relationships and property queries
Type modifications
Type transformations
(C++11)(deprecated in C++23)
(C++11)(deprecated in C++23)

(C++11)(until C++20)(C++17)
Compile-time rational arithmetic
Compile-time integer sequences
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.


[edit] Template parameters

T - a type to check

[edit] 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

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)
returns value
(public member function)

Member types

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

[edit] 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> {};

[edit] Example

#include <iomanip>
#include <iostream>
#include <type_traits>
#define IS_OBJECT(...) \
    std::cout << std::boolalpha << std::left << std::setw(9) << #__VA_ARGS__ \
              << (std::is_object_v<__VA_ARGS__> ? " is object\n" \
                                                : " is not an object\n")
int main()
    class cls {};
    IS_OBJECT( void );
    IS_OBJECT( int );
    IS_OBJECT( int& );
    IS_OBJECT( int* );
    IS_OBJECT( int*& );
    IS_OBJECT( cls );
    IS_OBJECT( cls& );
    IS_OBJECT( cls* );
    IS_OBJECT( int() );
    IS_OBJECT( int(*)() );
    IS_OBJECT( int(&)() );


void      is not an object
int       is object
int&      is not an object
int*      is object
int*&     is not an object
cls       is object
cls&      is not an object
cls*      is object
int()     is not an object
int(*)()  is object
int(&)()  is not an object

[edit] See also

checks if a type is a scalar type
(class template) [edit]
checks if a type is an array type
(class template) [edit]
checks if a type is a union type
(class template) [edit]
checks if a type is a non-union class type
(class template) [edit]