std::weak_ptr - Man Page
A non-owning observer for a pointer owned by a shared_ptr.
Synopsis
#include <memory>
Inherits std::__weak_ptr< _Tp, _Lp >.
Public Types
using element_type = typename remove_extent< _Tp >::type
Public Member Functions
template<typename _Yp , typename = _Constructible<const shared_ptr<_Yp>&>> weak_ptr (const shared_ptr< _Yp > &__r) noexcept
weak_ptr (const weak_ptr &) noexcept=default
template<typename _Yp , typename = _Constructible<const weak_ptr<_Yp>&>> weak_ptr (const weak_ptr< _Yp > &__r) noexcept
weak_ptr (weak_ptr &&) noexcept=default
template<typename _Yp , typename = _Constructible<weak_ptr<_Yp>>> weak_ptr (weak_ptr< _Yp > &&__r) noexcept
bool expired () const noexcept
shared_ptr< _Tp > lock () const noexcept
template<typename _Yp > _Assignable< const shared_ptr< _Yp > & > operator= (const shared_ptr< _Yp > &__r) noexcept
weak_ptr & operator= (const weak_ptr &__r) noexcept=default
template<typename _Yp > _Assignable< const weak_ptr< _Yp > & > operator= (const weak_ptr< _Yp > &__r) noexcept
weak_ptr & operator= (weak_ptr &&__r) noexcept=default
template<typename _Yp > _Assignable< weak_ptr< _Yp > > operator= (weak_ptr< _Yp > &&__r) noexcept
template<typename _Tp1 > bool owner_before (const __shared_ptr< _Tp1, _Lp > &__rhs) const noexcept
template<typename _Tp1 > bool owner_before (const __weak_ptr< _Tp1, _Lp > &__rhs) const noexcept
void reset () noexcept
void swap (__weak_ptr &__s) noexcept
long use_count () const noexcept
Related Functions
(Note that these are not member functions.)
template<typename _Tp > void swap (weak_ptr< _Tp > &__a, weak_ptr< _Tp > &__b) noexcept
Swap overload for weak_ptr.
Detailed Description
template<typename _Tp>
class std::weak_ptr< _Tp >"A non-owning observer for a pointer owned by a shared_ptr.
- Since
C++11
A weak_ptr provides a safe alternative to a raw pointer when you want a non-owning reference to an object that is managed by a shared_ptr.
Unlike a raw pointer, a weak_ptr can be converted to a new shared_ptr that shares ownership with every other shared_ptr that already owns the pointer. In other words you can upgrade from a non-owning 'weak' reference to an owning shared_ptr, without having access to any of the existing shared_ptr objects.
Also unlike a raw pointer, a weak_ptr does not become 'dangling' after the object it points to has been destroyed. Instead, a weak_ptr becomes expired and can no longer be converted to a shared_ptr that owns the freed pointer, so you cannot accidentally access the pointed-to object after it has been destroyed.
Definition at line 811 of file bits/shared_ptr.h.
Member Typedef Documentation
template<typename _Tp , _Lock_policy _Lp> using std::__weak_ptr< _Tp, _Lp >::element_type = typename remove_extent<_Tp>::type [inherited]
Definition at line 1985 of file shared_ptr_base.h.
Constructor & Destructor Documentation
template<typename _Tp > template<typename _Yp , typename = _Constructible<const weak_ptr<_Yp>&>> std::weak_ptr< _Tp >::weak_ptr (const weak_ptr< _Yp > & __r) [inline], [noexcept]
Definition at line 834 of file bits/shared_ptr.h.
template<typename _Tp > template<typename _Yp , typename = _Constructible<weak_ptr<_Yp>>> std::weak_ptr< _Tp >::weak_ptr (weak_ptr< _Yp > && __r) [inline], [noexcept]
Definition at line 840 of file bits/shared_ptr.h.
Member Function Documentation
template<typename _Tp , _Lock_policy _Lp> bool std::__weak_ptr< _Tp, _Lp >::expired () const [inline], [noexcept], [inherited]
Definition at line 2077 of file shared_ptr_base.h.
template<typename _Tp > template<typename _Yp > _Assignable< const weak_ptr< _Yp > & > std::weak_ptr< _Tp >::operator= (const weak_ptr< _Yp > & __r) [inline], [noexcept]
Definition at line 848 of file bits/shared_ptr.h.
template<typename _Tp > template<typename _Yp > _Assignable< weak_ptr< _Yp > > std::weak_ptr< _Tp >::operator= (weak_ptr< _Yp > && __r) [inline], [noexcept]
Definition at line 867 of file bits/shared_ptr.h.
template<typename _Tp , _Lock_policy _Lp> template<typename _Tp1 > bool std::__weak_ptr< _Tp, _Lp >::owner_before (const __weak_ptr< _Tp1, _Lp > & __rhs) const [inline], [noexcept], [inherited]
Definition at line 2087 of file shared_ptr_base.h.
template<typename _Tp , _Lock_policy _Lp> void std::__weak_ptr< _Tp, _Lp >::reset () [inline], [noexcept], [inherited]
Definition at line 2091 of file shared_ptr_base.h.
template<typename _Tp , _Lock_policy _Lp> void std::__weak_ptr< _Tp, _Lp >::swap (__weak_ptr< _Tp, _Lp > & __s) [inline], [noexcept], [inherited]
Definition at line 2095 of file shared_ptr_base.h.
template<typename _Tp , _Lock_policy _Lp> long std::__weak_ptr< _Tp, _Lp >::use_count () const [inline], [noexcept], [inherited]
Definition at line 2073 of file shared_ptr_base.h.
Author
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