Defined in header <type_traits> | ||
---|---|---|
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.
T | - | a type to check |
template< class T > inline constexpr bool is_abstract_v = is_abstract<T>::value; | (since C++17) |
value
[static] | true if T is an abstract class type , false otherwise (public static member constant) |
operator bool | converts the object to bool , returns value (public member function) |
operator()
(C++14) | returns value (public member function) |
Type | Definition |
---|---|
value_type | bool |
type | std::integral_constant<bool, value> |
#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
(C++11) | checks if a type is a non-union class type (class template) |
(C++11) | checks if a type is a polymorphic class type (class template) |
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