NAME¶

std::is_final - std::is_final

Synopsis¶

Defined in header <type_traits>
template< class T > (since C++14)
struct is_final;

std::is_final is a UnaryTypeTrait.

If T is a final class, provides the member constant value equal true. For any other
type, value is false.

If T is an incomplete class type, the behavior is undefined.

If the program adds specializations for std::is_final
or std::is_final_v
(since C++17), the behavior is undefined.

Template parameters¶

T - a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants¶

value true if T is a final class type, false otherwise
[static] (public static member constant)

Member functions¶

operator bool converts the object to bool, returns value
(public member function)
operator() returns value
(C++14) (public member function)

Member types¶

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

Notes¶

std::is_final is introduced by the resolution of LWG issue 2112.

A union can be declared final (and std::is_final will detect that), even though
unions cannot be used as bases in any case.

Feature-test macro Value Std Feature
__cpp_lib_is_final 201402L (C++14) std::is_final

Example¶

// Run this code

#include <type_traits>

class A {};
static_assert(std::is_final_v<A> == false);

class B final {};
static_assert(std::is_final_v<B> == true);

union U final
{
int x;
double d;
};
static_assert(std::is_final_v<U> == true);

int main()
{
}

See also¶

is_class checks if a type is a non-union class type
(C++11) (class template)
is_polymorphic checks if a type is a polymorphic class type
(C++11) (class template)