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std::weak_ptr

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C++
 
Утилиты библиотеки
 
Динамическое управление памятью
Низкий уровень управления памятью
Распределители
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Allocators
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allocator
allocator_traits(C++11)
allocator_arg_t(C++11)
allocator_arg(C++11)
uses_allocator(C++11)
scoped_allocator_adaptor(C++11)
Неинициализированные хранения
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Uninitialized storage
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uninitialized_copy
uninitialized_copy_n(C++11)
uninitialized_fill
uninitialized_fill_n
raw_storage_iterator
get_temporary_buffer
return_temporary_buffer
Умные указатели
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Smart pointers
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unique_ptr(C++11)
shared_ptr(C++11)
weak_ptr(C++11)
auto_ptr(устарело)
owner_less(C++11)
enable_shared_from_this(C++11)
bad_weak_ptr(C++11)
default_delete(C++11)
Поддержка сборки мусора
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Garbage collection support
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declare_reachable(C++11)
undeclare_reachable(C++11)
declare_no_pointers(C++11)
undeclare_no_pointers(C++11)
pointer_safety(C++11)
get_pointer_safety(C++11)
Разное
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Miscellaneous
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pointer_traits(C++11)
addressof(C++11)
align(C++11)
C Library
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C Library
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std::weak_ptr
Член функций
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Member functions
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weak_ptr::weak_ptr
weak_ptr::~weak_ptr
weak_ptr::operator=
Модификаторы
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Modifiers
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weak_ptr::reset
weak_ptr::swap
Наблюдателей
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Observers
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weak_ptr::use_count
weak_ptr::expired
weak_ptr::lock
weak_ptr::owner_before
Не являющиеся членами функций
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Non-member functions
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std::swap
 
Заголовочный файл <memory>
template< class T > class weak_ptr;
 (начиная с C++11)
std::weak_ptr является смарт-указатель, который содержит, не владеющего ("слабые") ссылку на объект, который находится в ведении std::shared_ptr. Оно должно быть преобразовано в std::shared_ptr, чтобы получить доступ указанный объект.
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 моделей временное владение., когда объект должен быть доступен только если она существует, и он может быть удален в любое время кто-то другой, std::weak_ptr используется для отслеживания объекта, и он превращается в std::shared_ptr считать временное владение. Если исходный std::shared_ptr разрушен в это время, время жизни объекта продлевается до временного std::shared_ptr разрушен, а.
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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Кроме того, std::weak_ptr используется для разорвать циклические ссылки из std::shared_ptr.
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In addition, std::weak_ptr is used to break circular references of std::shared_ptr.
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Содержание

[править] Член типов

Член типа
Original:
Member type
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 Definition
element_type T

[править] Член функций
создает новый weak_ptr
Original:
creates a new weak_ptr
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(public функция-член) [edit]
разрушает weak_ptr
Original:
destroys a weak_ptr
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(public функция-член) [edit]
назначает weak_ptr
Original:
assigns the weak_ptr
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(public функция-член) [edit]
Модификаторы
Original:
Modifiers
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освобождает собственности на управляемый объект
Original:
releases the ownership of the managed object
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(public функция-член) [edit]
свопы управляемых объектов
Original:
swaps the managed objects
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(public функция-член) [edit]
Наблюдателей
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Observers
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возвращает количество объектов, которые shared_ptr управлять объектом
Original:
returns the number of shared_ptr objects that manage the object
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(public функция-член) [edit]
проверяет, является ли указанный объект уже был удален
Original:
checks whether the referenced object was already deleted
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(public функция-член) [edit]
создает shared_ptr, которая управляет указанный объект
Original:
creates a shared_ptr that manages the referenced object
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(public функция-член) [edit]
предоставляет владельцу на основе упорядочения слабые указатели
Original:
provides owner-based ordering of weak pointers
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(public функция-член) [edit]

[править] Не являющиеся членами функций

(C++11)
Специализируется std::swap алгоритм
Original:
specializes the std::swap algorithm
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(шаблон функции) [edit]

[править] Пример

Демонстрирует как замок используется для обеспечения действия указателя .
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();
}

Вывод: 

42
gw is expired
Источник — «http://ru.cppreference.com/mwiki/index.php?title=cpp/memory/weak_ptr&oldid=27645»