std::is_abstract – cppreference.com

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definiert in Header `<type_traits>`

`template< class T > struct is_abstract;`		(seit C++11)

Wenn T eine abstrakte Klasse (das heißt, eine Klasse, oder erklärt, erbt mindestens eine rein virtuelle Funktion) ist, stellt das Mitglied konstanten value gleich true. Für jede andere Art, value ist false .

Original:

If T is an abstract class (that is, a 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.

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Inherited from std::integral_constant

Member constants


	`true` wenn `T` is an abstract class type , `false` anders Original: `true` if `T` is an abstract class type , `false` otherwise The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (public static Mitglied konstanten)

Member functions


	wandelt das Objekt `bool`, gibt `value` Original: converts the object to `bool`, returns `value` The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (öffentliche Elementfunktion)

Member types


Type Original: Type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	Definition

`value_type`	`bool`

`type`	`std::integral_constant<bool, value>`

Notes

Abstrakte Klassen können nur als Basisklassen verwendet werden; keine Objekte einer abstrakten Klasse Typ kann außer in Form von Basisklasse Unterobjekte erstellt werden .

Original:

Abstract classes may only be used as base classes; no objects of an abstract class type can be created except in form of base class subobjects.

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Eine abstrakte Klasse kann von einer Klasse, die nicht abstrakt ist, wenn eine rein virtuelle Funktion überschreibt eine virtuelle Funktion, die nicht rein abgeleitet werden .

Original:

An abstract class may be derived from a class that is not abstract if a pure virtual function overrides a virtual function that is not pure.

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Beispiel

#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:

Siehe auch


	checks if a type is a class type (but not union type) (Klassen-Template) [edit]

	prüft, ob ein Typ ist polymorphe Klasse Typ Original: checks if a type is polymorphic class type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Klassen-Template) [edit]