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std::is_constructible, std::is_trivially_constructible, std::is_nothrow_constructible – cppreference.com

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<metanoindex/>

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definiert in Header

<type_traits>

template< class T, class... Args > struct is_constructible;

 (1) (seit C++11)

template< class T, class... Args > struct is_trivially_constructible;

 (2) (seit C++11)

template< class T, class... Args > struct is_nothrow_constructible;

 (3) (seit C++11)

1)

Wenn der Ausdruck T obj(arg1, arg2, ... argN); ist wohlgeformt, da rvalue Verweise auf Args... als Argumente, bietet das Mitglied konstanten value gleich true. Für jede andere Art, value ist false .

Original:

If the expression T obj(arg1, arg2, ... argN); is well-formed, given rvalue references to Args... as arguments, provides the member constant value equal true. For any other type, value is false.

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2)

wie 1), aber der Konstruktor Ausdruck nicht nennen jede Operation, die nicht trivial ist .

Original:

same as 1), but the constructor expression does not call any operation that is not trivial.

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3)

Gleiche wie 1), aber der Konstruktor Expression noexcept .

Original:

same as 1), but the constructor expression is noexcept.

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Inherited from std::integral_constant

Member constants

true wenn T is constructible from Args... , false anders

Original:

true if T is constructible from Args... , false otherwise

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(public static Mitglied konstanten)

Member functions

wandelt das Objekt bool, gibt value

Original:

converts the object to bool, returns value

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(öffentliche Elementfunktion)

Member types

Type

Original:

Type

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 Definition
value_type bool
type std::integral_constant<bool, value>

Beispiel

#include <iostream>
#include <type_traits>

class Foo {
    int v1;
    double v2;
 public:
    Foo(int n) : v1(n), v2() {}
    Foo(int n, double f) noexcept : v1(n), v2(f) {}
};

int main() {
    std::cout << "Foo is ...\n" << std::boolalpha
              << "\tTrivially-constructible from const Foo&? "
              << std::is_trivially_constructible<Foo, const Foo&>::value << '\n'
              << "\tTrivially-constructible from int? "
              << std::is_trivially_constructible<Foo, int>::value << '\n'
              << "\tConstructible from int? "
              << std::is_constructible<Foo, int>::value << '\n'
              << "\tNothrow-constructible from int? "
              << std::is_nothrow_constructible<Foo, int>::value << '\n'
              << "\tNothrow-constructible from int and double? "
              << std::is_nothrow_constructible<Foo, int, double>::value << '\n';
}

Output: 

Foo is ...
        Trivially-constructible from const Foo&? true
        Trivially-constructible from int? false
        Constructible from int? true
        Nothrow-constructible from int? false
        Nothrow-constructible from int and double? true

Siehe auch

prüft, ob ein Typ hat einen Default-Konstruktor

Original:

checks if a type has a default constructor

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(Klassen-Template) [edit]

prüft, ob ein Typ hat einen Copy-Konstruktor

Original:

checks if a type has a copy constructor

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(Klassen-Template) [edit]

prüft, ob ein Typ hat einen Umzug Konstruktor

Original:

checks if a type has a move constructor

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(Klassen-Template) [edit]
prüft, ob der angegebene Typ allokatorgestützte Erzeugung unterstützt.
(Klassen-Template) [edit]