NAME¶

std::is_abstract - std::is_abstract

Synopsis¶

Defined in header <type_traits>
template< class T > (since C++11)
struct is_abstract;

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 to 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.

The behavior of a program that adds specializations for is_abstract
or is_abstract_v
(since C++17) is undefined.

Template parameters¶

T - a type to check

Helper variable template

template< class T > (since C++17)
inline constexpr bool is_abstract_v = is_abstract<T>::value;

Inherited from std::integral_constant

Member constants¶

value true if T is an abstract class type , false otherwise
[static] (public static member constant)

Member functions¶

operator bool converts the object to bool, returns value
(public member function)
operator() returns value
(C++14) (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¶

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