From cppreference.com
template<classT>structis_object;(since C++11)std::is_object is a
.
If T is an
(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.
If the program adds specializations for std::is_object or std::is_object_v, the behavior is undefined.
Template parameters
T - a type to check Helper variable template
template<classT>constexprboolis_object_v=is_object<T>::value;(since C++17)Inherited from
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_typebooltypestd::integral_constant<bool,value>Possible implementation
template<classT>structis_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<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")intmain(){classcls{};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(&)());}Output:
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 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 a union type
(class template)
(C++11)
checks if a type is a non-union class type
(class template)
(C++26)
checks if reflected type is an object type
(function)