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std::is_final

From cppreference.com
< cpp‎ | types
 
 
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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 (that is, a class declared with the final specifier), provides the member constant value equal true. For any other type, value is false.

If T is a class type, T shall be a complete type; otherwise, the behavior is undefined.

The behavior of a program that adds specializations for std::is_final or std::is_final_v(since C++17) is undefined.

Contents

[edit] Template parameters

T - a type to check

[edit] Helper variable template

template< class T >
inline 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>

[edit] Notes

Final classes cannot be used as base classes.

A union can be marked 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

[edit] Example

#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()
{
}

[edit] See also

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