std::is_final

 

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

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

Inherited from std::integral_constant

Member constants

value [static]

true if T is a final class 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>

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