std::is_final
From cppreference.com
| 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()
{
}