std::is_object

 

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

std::is_object is a UnaryTypeTrait.

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.

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<class T > constexprbool 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

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")   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(&)());}

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

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