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std::is_move_constructible, std::is_trivially_move_constructible, std::is_nothrow_move_constructible - cppreference.com

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Elemento definito nell'header

<type_traits>

template< class T > struct is_move_constructible;

 (1) (dal C++11)

template< class T > struct is_trivially_move_constructible;

 (2) (dal C++11)

template< class T > struct is_nothrow_move_constructible;

 (3) (dal C++11)

1)

Verifica se un tipo è MoveConstructible, cioè ha un costruttore accessibile mossa esplicita o implicita. Se la condizione è soddisfatta, un membro costante value true parità è previsto, in caso contrario è value false.

Original:

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

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2)

Uguale a 1), ma l'espressione di costruzione mossa non richiede qualsiasi operazione che non è banale.

Original:

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

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3)

Uguale a 1), ma l'espressione di costruzione mossa viene noexcept.

Original:

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

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Inherited from std::integral_constant

Member constants

true se T is move-constructible , false altrimenti

Original:

true if T is move-constructible , false otherwise

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(pubblico membro statico costante)

Member functions

converte l'oggetto in bool, restituisce value

Original:

converts the object to bool, returns value

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(metodo pubblico)

Member types

Tipo

Original:

Type

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

Note

Spostare i costruttori di solito sono noexcept, in quanto altrimenti sono inutilizzabili in qualsiasi codice che fornisce garanzia forte eccezione.

Original:

Move constructors are usually noexcept, since otherwise they are unusable in any code that provides strong exception guarantee.

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Possibile implementazione

template<class T>
struct is_move_constructible :
        std::is_constructible<T, typename std::add_rvalue_reference<T>::type> {};

template<class T>
struct is_trivially_move_constructible :
       std::is_trivially_constructible<T, typename std::add_rvalue_reference<T>::type> {};

template<class T>
struct is_nothrow_move_constructible :
       std::is_nothrow_constructible<T, typename std::add_rvalue_reference<T>::type> {};

Esempio

#include <iostream>
#include <type_traits>

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

int main() {
    std::cout << std::boolalpha << "Ex1 is move-constructible? "
              << std::is_move_constructible<Ex1>::value << '\n'
              << "Ex1 is trivially move-constructible? "
              << std::is_trivially_move_constructible<Ex1>::value << '\n'
              << "Ex1 is nothrow move-constructible? "
              << std::is_nothrow_move_constructible<Ex1>::value << '\n'
              << "Ex2 is trivially move-constructible? "
              << std::is_trivially_move_constructible<Ex2>::value << '\n'
              << "Ex2 is nothrow move-constructible? "
              << std::is_nothrow_move_constructible<Ex2>::value << '\n';
}

Output: 

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

Vedi anche

Verifica se un tipo ha un costruttore per argomenti specifici

Original:

checks if a type has a constructor for specific arguments

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(classe template) [modifica]

Verifica se un tipo ha un costruttore di default

Original:

checks if a type has a default constructor

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(classe template) [modifica]

Verifica se un tipo ha un costruttore di copia

Original:

checks if a type has a copy constructor

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(classe template) [modifica]

ottiene un riferimento rvalue se il costruttore mossa non genera

Original:

obtains an rvalue reference if the move constructor does not throw

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(funzione di modello) [modifica]