std::weak_ptr::expired

 

C++

Язык

Понятия (концепции)

Утилиты

Строки

Контейнеры

Алгоритмы

Итераторы

Работа с числами

Ввод / вывод

Локализация

Регулярные выражения (C++11)

Атомарные примитивы (C++11)

Потоки (C++11)

 

Утилиты библиотеки

Поддежка типов (базовые типы, RTTI, type traits)

Динамическое управление памятью

Обработка ошибок

Управление жизненным циклом программы

Функции с переменным числом аргументов

Дата и время

Функциональные объекты

initializer_list (C++11)

bitset

hash (C++11)

Реляционные операторы

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Пары и кортежи

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Обмен, передача и перемещение

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Динамическое управление памятью

Низкий уровень управления памятью
Распределители Original: Allocators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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 Original: Uninitialized storage The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
uninitialized_copy
uninitialized_copy_n (C++11)
uninitialized_fill
uninitialized_fill_n
raw_storage_iterator
get_temporary_buffer
return_temporary_buffer
Умные указатели Original: Smart pointers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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 Original: Garbage collection support The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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 Original: Miscellaneous The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
pointer_traits (C++11)
addressof (C++11)
align (C++11)
C Library Original: C Library The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
malloc calloc	realloc free

 

std::weak_ptr

Член функций Original: Member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

weak_ptr::weak_ptr

weak_ptr::~weak_ptr

weak_ptr::operator=

Модификаторы Original: Modifiers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

weak_ptr::reset

weak_ptr::swap

Наблюдателей Original: Observers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

weak_ptr::use_count

weak_ptr::expired

weak_ptr::lock

weak_ptr::owner_before

Не являющиеся членами функций Original: Non-member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

std::swap

 

bool expired() const;		(начиная с C++11)

Проверяет, является ли управляемый объект уже удален. Эквивалент use_count() == 0.

Original:

Checks whether the managed object has already been deleted. Equivalent to use_count() == 0.

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Параметры

(Нет)

Original:

(none)

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Возвращаемое значение

true если управляемый объект уже удален, false иначе.

Original:

true if the managed object has already been deleted, false otherwise.

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Исключения

noexcept-спецификация:  

noexcept

  (начиная с C++11)

Notes

expired() может быть быстрее, чем use_count().

Original:

expired() may be faster than use_count().

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Пример

Демонстрирует истекшим используется для проверки действия указателей .

Original:

Demonstrates how expired is used to check validity of the pointer.

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#include <iostream>
#include <memory>
 
std::weak_ptr<int> gw;
 
void f()
{
    if (!gw.expired()) {
    std::cout << "gw is valid\n";
    }
    else {
        std::cout << "gw is expired\n";
    }
}
 
int main()
{
    {
        auto sp = std::make_shared<int>(42);
    gw = sp;
 
    f();
    }
 
    f();
}

Вывод:

gw is valid
gw is expired

См. также

lock	создает shared_ptr, которая управляет указанный объект Original: creates a shared_ptr that manages the referenced object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (public функция-член)
use_count	возвращает количество объектов, которые shared_ptr управлять объектом Original: returns the number of shared_ptr objects that manage the object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (public функция-член)