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std::is_abstract

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< cpp‎ | types

 
 
 
Soutien aux types fondamentaux
Les types de base
Original:
Basic types
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Types fondamentaux
Fixe les types entiers largeur (C++11)
Limites numériques
Original:
Numeric limits
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numeric_limits
C numérique limite interface
Informations sur le type d'exécution
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Runtime type information
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Caractères de type
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Type traits
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Catégories de type primaire
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Primary type categories
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is_void (C++11)
is_array (C++11)
is_pointer (C++11)
is_enum (C++11)
is_union (C++11)
is_class (C++11)
is_function (C++11)
is_object (C++11)
is_scalar (C++11)
is_compound (C++11)
is_integral (C++11)
is_floating_point (C++11)
is_fundamental (C++11)
is_arithmetic (C++11)
is_reference (C++11)
is_lvalue_reference (C++11)
is_rvalue_reference (C++11)
is_member_pointer (C++11)
is_member_object_pointer (C++11)
is_member_function_pointer (C++11)
Les propriétés du type
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Type properties
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is_const (C++11)
is_volatile (C++11)
is_pod (C++11)
is_empty (C++11)
is_polymorphic (C++11)
is_abstract (C++11)
Opérations prises en charge
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Supported operations
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is_constructible
is_trivially_constructible
is_nothrow_constructible
(C++11)
(C++11)
(C++11)
is_default_constructible
is_trivially_default_constructible
is_nothrow_default_constructible
(C++11)
(C++11)
(C++11)
is_copy_constructible
is_trivially_copy_constructible
is_nothrow_copy_constructible
(C++11)
(C++11)
(C++11)
is_move_constructible
is_trivially_move_constructible
is_nothrow_move_constructible
(C++11)
(C++11)
(C++11)
is_assignable
is_trivially_assignable
is_nothrow_assignable
(C++11)
(C++11)
(C++11)
is_copy_assignable
is_trivially_copy_assignable
is_nothrow_copy_assignable
(C++11)
(C++11)
(C++11)
is_move_assignable
is_trivially_move_assignable
is_nothrow_move_assignable
(C++11)
(C++11)
(C++11)
is_destructible
is_trivially_destructible
is_nothrow_destructible
(C++11)
(C++11)
(C++11)
has_virtual_destructor (C++11)
Les relations et les requêtes de propriété
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Relationships and property queries
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is_same (C++11)
is_base_of (C++11)
is_convertible (C++11)
alignment_of (C++11)
rank (C++11)
extent (C++11)
Modifications de type
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Type modifications
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remove_cv
remove_const
remove_volatile
(C++11)
(C++11)
(C++11)
add_cv
add_const
add_volatile
(C++11)
(C++11)
(C++11)
make_signed (C++11)
make_unsigned (C++11)
Transformations de type
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Type transformations
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aligned_storage (C++11)
aligned_union (C++11)
decay (C++11)
enable_if (C++11)
conditional (C++11)
common_type (C++11)
underlying_type (C++11)
result_of (C++11)
Tapez constantes traits
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Type trait constants
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integral_constant (C++11)
 
Defined in header <type_traits>
template< class T >
struct is_abstract;
(depuis C++11)
Si T est une classe abstraite (c'est-à-dire une classe qui hérite déclare ou au moins une fonction virtuelle pure), fournit du membre de constante value true égale. Pour tout autre type, value est 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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Sommaire

Inherited from std::integral_constant

Member constants

value
[
statique
Original:
static
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]
true si T is an abstract class type , false autrement
Original:
true if T is an abstract class type , false otherwise
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(constante membre statique publique)

Member functions

operator bool
convertit l'objet en bool, retourne value
Original:
converts the object to bool, returns value
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(fonction membre publique)

Member types

Type d'
Original:
Type
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Definition
value_type bool
type std::integral_constant<bool, value>

[modifier] Notes

Les classes abstraites ne peuvent être utilisés comme classes de base, pas des objets d'un type de classe abstraite ne peut être créé que sous forme de sous-objets de classe de base .
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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Une classe abstraite peut être dérivée d'une classe qui n'est pas abstraite si une fonction virtuelle pure remplace une fonction virtuelle qui n'est pas pur .
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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[modifier] Exemple

#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';
}

Résultat :

false
false
true
true

[modifier] Voir aussi

(C++11)
checks if a type is a class type (but not union type)
(classe générique) [edit]
vérifie si un type est le type de classe polymorphique
Original:
checks if a type is polymorphic class type
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(classe générique) [edit]