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std::weak_ptr

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< cpp‎ | memory

 
 
Utilità libreria
Tipo di supporto (basic types, RTTI, type traits)
Gestione della memoria dinamica
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Programma di utilità
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Data e ora
Funzione oggetti
initializer_list(C++11)
bitset
hash(C++11)
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Relational operators
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rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
Coppie e tuple
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Pairs and tuples
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pair
tuple(C++11)
piecewise_construct_t(C++11)
piecewise_construct(C++11)
Swap, in avanti e spostare
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Swap, forward and move
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swap
forward(C++11)
move(C++11)
move_if_noexcept(C++11)
declval(C++11)
 
Gestione della memoria dinamica
Basso livello di gestione della memoria
Allocatori
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Allocators
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allocator_traits(C++11)
allocator_arg_t(C++11)
allocator_arg(C++11)
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Non inizializzata stoccaggio
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Uninitialized storage
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uninitialized_copy
uninitialized_copy_n(C++11)
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Puntatori intelligenti
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Smart pointers
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unique_ptr(C++11)
shared_ptr(C++11)
weak_ptr(C++11)
auto_ptr(deprecato)
owner_less(C++11)
enable_shared_from_this(C++11)
bad_weak_ptr(C++11)
default_delete(C++11)
Garbage collection supporto
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Garbage collection support
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declare_reachable(C++11)
undeclare_reachable(C++11)
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pointer_traits(C++11)
addressof(C++11)
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C Library
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C Library
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std::weak_ptr
Membri funzioni
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Member functions
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weak_ptr::weak_ptr
weak_ptr::~weak_ptr
weak_ptr::operator=
Modificatori
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Modifiers
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weak_ptr::reset
weak_ptr::swap
Osservatori
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Observers
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weak_ptr::use_count
weak_ptr::expired
weak_ptr::lock
weak_ptr::owner_before
Non membri funzioni
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Non-member functions
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std::swap
 
Defined in header <memory>
template< class T > class weak_ptr;
(dal C++11)
std::weak_ptr è un puntatore intelligente che contiene un non proprietario ("debole"), riferimento a un oggetto gestito da std::shared_ptr. Deve essere convertito in std::shared_ptr per accedere l'oggetto di riferimento.
Original:
std::weak_ptr is a smart pointer that holds a non-owning ("weak") reference to an object that is managed by std::shared_ptr. It must be converted to std::shared_ptr in order to access the referenced object.
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std::weak_ptr modelli temporanea di proprietà:. quando un oggetto ha bisogno di essere accessibile solo se esiste, e può essere cancellato in qualsiasi momento da un altro utente, std::weak_ptr viene utilizzato per monitorare l'oggetto, ed è convertito al std::shared_ptr di assumere proprietà temporanea. Se il std::shared_ptr originale viene distrutto in questo momento, la vita dell'oggetto è prorogato fino al std::shared_ptr temporaneo si distrugge anche la.
Original:
std::weak_ptr models temporary ownership: when an object needs to be accessed only if it exists, and it may be deleted at any time by someone else, std::weak_ptr is used to track the object, and it is converted to std::shared_ptr to assume temporary ownership. If the original std::shared_ptr is destroyed at this time, the object's lifetime is extended until the temporary std::shared_ptr is destroyed as well.
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Inoltre, std::weak_ptr viene utilizzato per interrompere i riferimenti circolari di std::shared_ptr.
Original:
In addition, std::weak_ptr is used to break circular references of std::shared_ptr.
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Indice

[modifica] Membri tipi

Membro tipo
Original:
Member type
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Definition
element_type T

[modifica] Membri funzioni

crea un nuovo weak_ptr
Original:
creates a new weak_ptr
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(membro pubblico funzione) [edit]
distrugge un weak_ptr
Original:
destroys a weak_ptr
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(membro pubblico funzione) [edit]
assegna il weak_ptr
Original:
assigns the weak_ptr
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(membro pubblico funzione) [edit]
Modificatori
Original:
Modifiers
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rilascia la proprietà dell'oggetto gestito
Original:
releases the ownership of the managed object
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(membro pubblico funzione) [edit]
swap gli oggetti gestiti
Original:
swaps the managed objects
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(membro pubblico funzione) [edit]
Osservatori
Original:
Observers
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restituisce il numero di oggetti shared_ptr che gestiscono l'oggetto
Original:
returns the number of shared_ptr objects that manage the object
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(membro pubblico funzione) [edit]
Verifica se l'oggetto di riferimento è già stato cancellato
Original:
checks whether the referenced object was already deleted
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(membro pubblico funzione) [edit]
crea un shared_ptr che gestisce l'oggetto indicato
Original:
creates a shared_ptr that manages the referenced object
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(membro pubblico funzione) [edit]
fornisce proprietario basato ordinamento di puntatori deboli
Original:
provides owner-based ordering of weak pointers
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(membro pubblico funzione) [edit]

[modifica] Non membri funzioni

specializzata l'algoritmo std::swap
Original:
specializes the std::swap algorithm
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(funzione di modello) [edit]

[modifica] Esempio

Dimostra come blocco viene utilizzato per garantire la validità del puntatore .
Original:
Demonstrates how lock is used to ensure validity of the pointer.
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#include <iostream>
#include <memory>
 
std::weak_ptr<int> gw;
 
void f()
{
    if (auto spt = gw.lock()) { // Has to be copied into a shared_ptr before usage
	std::cout << *spt << "\n";
    }
    else {
        std::cout << "gw is expired\n";
    }
}
 
int main()
{
    {
        auto sp = std::make_shared<int>(42);
	gw = sp;
 
	f();
    }
 
    f();
}

Output:

42
gw is expired