std::is_abstract
From cppreference.com
| Defined in header <type_traits>
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| template< class T > struct is_abstract; |
(since C++11) | |
If T is an abstract class (that is, a non-union class that declares or inherits at least one pure virtual function), provides the member constant value equal true. For any other type, value is false.
If T is a non-union class type, T shall be a complete type; otherwise, the behavior is undefined.
Template parameters
| T | - | a type to check |
Helper variable template
| template< class T > inline constexpr bool is_abstract_v = is_abstract<T>::value; |
(since C++17) | |
Inherited from std::integral_constant
Member constants
| value [static] |
true if T is an abstract 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> |
Example
Run this code
#include <iostream> #include <type_traits> struct A { int m; }; struct B { virtual void foo(); }; struct C { virtual void foo() = 0; }; struct D : C {}; int main() { std::cout << std::boolalpha; std::cout << std::is_abstract<A>::value << '\n'; std::cout << std::is_abstract<B>::value << '\n'; std::cout << std::is_abstract<C>::value << '\n'; std::cout << std::is_abstract<D>::value << '\n'; }
Output:
false false true true
See also
| (C++11) |
checks if a type is a non-union class type (class template) |
| (C++11) |
checks if a type is polymorphic class type (class template) |