std::is_copy_constructible, std::is_trivially_copy_constructible, std::is_nothrow_copy_constructible – cppreference.com

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definiert in Header `<type_traits>`

`template< class T > struct is_copy_constructible;`	(1)	(seit C++11)

`template< class T > struct is_trivially_copy_constructible;`	(2)	(seit C++11)

`template< class T > struct is_nothrow_copy_constructible;`	(3)	(seit C++11)

Prüft, ob eine Art CopyConstructible ist, dh eine zugängliche explizite oder implizite Copy-Konstruktor. Wenn die Bedingung erfüllt ist, ein Mitglied konstanten value gleich true bereitgestellt wird, sonst value ist false .

Original:

Checks whether a type is CopyConstructible, i.e. has an accessible explicit or implicit copy constructor. If the requirement is met, a member constant value equal true is provided, otherwise value is false.

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Same as (1), aber die Kopie Konstruktor Ausdruck nicht nennen jede Operation, die nicht trivial ist .

Original:

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

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Same as (1), aber die Kopie Konstruktor Ausdruck noexcept .

Original:

Same as (1), but the copy constructor expression is noexcept.

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Inherited from std::integral_constant

Member constants


	`true` wenn `T` is copy-constructible , `false` anders Original: `true` if `T` is copy-constructible , `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>`

Mögliche Implementierung

template<class T>
struct is_copy_constructible :
    std::is_constructible<T, const typename std::add_lvalue_reference<T>::type> {};

template<class T>
struct is_trivially_copy_constructible :
    std::is_trivially_constructible<T, const typename std::add_lvalue_reference<T>::type> {};

template<class T>
struct is_nothrow_copy_constructible :
    std::is_nothrow_constructible<T, const typename std::add_lvalue_reference<T>::type> {};

Beispiel

#include <iostream>
#include <type_traits>

struct Ex1 {
    std::string str; // member has a non-trivial copy ctor
};
struct Ex2 {
    int n;
    Ex2(const Ex2&) = default; // trivial and non-throwing
};

int main() {
    std::cout << std::boolalpha << "Ex1 is copy-constructible? "
              << std::is_copy_constructible<Ex1>::value << '\n'
              << "Ex1 is trivially copy-constructible? "
              << std::is_trivially_copy_constructible<Ex1>::value << '\n'
              << "Ex2 is trivially copy-constructible? "
              << std::is_trivially_copy_constructible<Ex2>::value << '\n'
              << "Ex2 is nothrow copy-constructible? "
              << std::is_nothrow_copy_constructible<Ex2>::value << '\n';
}

Output:

Ex1 is copy-constructible? true
Ex1 is trivially copy-constructible? false
Ex2 is trivially copy-constructible? true
Ex2 is nothrow copy-constructible? true

Siehe auch


is_constructible is_trivially_constructible is_nothrow_constructible (C++11) (C++11) (C++11)	prüft, ob ein Typ hat einen Konstruktor für Argumente Original: checks if a type has a constructor for specific arguments 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]

is_default_constructible is_trivially_default_constructible is_nothrow_default_constructible (C++11) (C++11) (C++11)	prüft, ob ein Typ hat einen Default-Konstruktor Original: checks if a type has a default constructor 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]

is_move_constructible is_trivially_move_constructible is_nothrow_move_constructible (C++11) (C++11) (C++11)	prüft, ob ein Typ hat einen Umzug Konstruktor Original: checks if a type has a move constructor 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]