copy initialization

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Syntaxe

Explication

• Si T est un type de classe et le type de other est cv-inconditionnel de la version T ou une classe drive de T, les constructeurs de T sont examines et la meilleure correspondance est choisi par la rsolution de surcharge. Le constructeur est alors appele pour initialiser l'objet .

  Original:

  If T is a class type and the type of other is cv-unqualified version of T or a class derived from T, the constructors of T are examined and the best match is selected by overload resolution. The constructor is then called to initialize the object.

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• Si T est un type de classe et le type de other est diffrent, ou si T n'est pas de type classe, mais le type de other est un type de classe, des squences dfinies par l'utilisateur de conversion qui peut convertir le type de other T sont examins et le meilleur on est slectionn grce la rsolution de surcharge. Le rsultat de la conversion, qui est une prvalue temporaire du type de destination, est ensuite utilis pour diriger-initialiser l'objet. La dernire tape est gnralement limin et le rsultat de la fonction de conversion est construit directement dans la mmoire alloue pour l'objet cible, mais le constructeur de copie est ncessaire pour tre accessible mme si elle n'est pas utilise .

  Original:

  If T is a class type, and the type of other is different, or if T is non-class type, but the type of other is a class type, des squences dfinies par l'utilisateur de conversion that can convert from the type of other to T are examined and the best one is selected through overload resolution. The result of the conversion, which is a prvalue temporary of the destination type, is then used to diriger-initialiser the object. The last step is usually limin and the result of the conversion function is constructed directly in the memory allocated for the target object, but the copy constructor is required to be accessible even though it's not used.

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• Dans le cas contraire (si aucun T ni le type de other sont les types de classes), conversions standard sont utiliss, si ncessaire, pour convertir la valeur de other la version cv-inconditionnel de T .

  Original:

  Otherwise (if neither T nor the type of other are class types), conversions standard are used, if necessary, to convert the value of other to the cv-unqualified version of T.

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Notes

Exemple

#include <string>
#include <utility>
#include <memory>

int main()
{
    std::string s = "test"; // OK: constructor is non-explicit
    std::string s2 = std::move(s); // this copy-initialization performs a move

//  std::unique_ptr<int> p = new int(1); // error: constructor is explicit
    std::unique_ptr<int> p(new int(1)); // OK: direct-initialization

    int n = 3.14;    // floating-integral conversion
    const int b = n; // const doesn't matter
    int c = b;       // ...either way
}

Voir aussi

• initialisation par dfaut
• initialisation directe
• initialisation d'agrgats
• liste d'initialisation