# std::is_object

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< cpp‎ | types

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 > 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

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)

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