std::shared_ptr::owner_before

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shared_ptr::owner_before

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template< class T > bool owner_before( const shared_ptr<T>& other) const;
template< class T > bool owner_before( const std::weak_ptr<T>& other) const;

Vérifie si cette shared_ptr précède other dans la mise en œuvre définies propriétaire (par opposition à la valeur) de commande. L'ordre est telle que deux pointeurs intelligents comparer équivalent que si elles sont vides ou si ils ont tous deux le même objet propre, même si les valeurs des pointeurs obtenus par get () sont différentes (par exemple, parce qu'ils renvoient à des sous-objets différents dans le même objet)

Original:

Checks whether this shared_ptr precedes other in implementation defined owner-based (as opposed to value-based) order. The order is such that two smart pointers compare equivalent only if they are both empty or if they both own the same object, even if the values of the pointers obtained by get() are different (e.g. because they point at different subobjects within the same object)

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Cet ordre est utilisé pour faire partager pointeurs faibles et utilisable en tant que clés dans des conteneurs associatifs, généralement au moyen std::owner_less .

Original:

This ordering is used to make shared and weak pointers usable as keys in associative containers, typically through std::owner_less.

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Paramètres

other

-

la std::shared_ptr ou std::weak_ptr à comparer Original: the std::shared_ptr or std::weak_ptr to be compared The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Retourne la valeur

true si *this précède other, false autrement. Implémentations communes comparer les adresses des blocs de commande .

Original:

true if *this precedes other, false otherwise. Common implementations compare the addresses of the control blocks.

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Exemple

#include <iostream>
#include <memory>
 
struct Foo {
    int n1;
    int n2; 
    Foo(int a, int b) : n1(a), n2(b) {}
};
int main()
{   
    auto p1 = std::make_shared<Foo>(1, 2);
    std::shared_ptr<int> p2(p1, &p1->n1);
    std::shared_ptr<int> p3(p1, &p1->n2);

    std::cout << std::boolalpha
              << "p2 < p3 " << (p2 < p3) << '\n'
              << "p3 < p2 " << (p3 < p2) << '\n'
              << "p2.owner_before(p3) " << p2.owner_before(p3) << '\n'
              << "p3.owner_before(p2) " << p3.owner_before(p2) << '\n';

    std::weak_ptr<int> w2(p2);
    std::weak_ptr<int> w3(p3);
    std::cout 
//              << "w2 < w3 " << (w2 < w3) << '\n'  // won't compile 
//              << "w3 < w2 " << (w3 < w2) << '\n'  // won't compile
              << "w2.owner_before(w3) " << w2.owner_before(w3) << '\n'
              << "w3.owner_before(w2) " << w3.owner_before(w2) << '\n';

}

Résultat :

p2 < p3 true
p3 < p2 false
p2.owner_before(p3) false
p3.owner_before(p2) false
w2.owner_before(w3) false
w3.owner_before(w2) false

Voir aussi

owner_less (C++11)	offre mixte de type propriétaire-base ordonnancement des pointeurs partagés et faible Original: provides mixed-type owner-based ordering of shared and weak pointers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (classe générique)