std::weak_ptr

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std::weak_ptr
Member functions weak_ptr::weak_ptr weak_ptr::~weak_ptr weak_ptr::operator= Modifiers weak_ptr::reset weak_ptr::swap Observers weak_ptr::use_count weak_ptr::expired weak_ptr::lock weak_ptr::owner_before Non-member functions std::swap

Defined in header <memory>
template< class T > class weak_ptr;		(since C++11)

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.

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.

In addition, std::weak_ptr is used to break circular references of std::shared_ptr.

Contents 1 Member types 2 Member functions 2.1 Modifiers 2.2 Observers 3 Non-member functions

[edit] Member types

Member type	Definition
element_type	T

[edit] Member functions

(constructor)	creates a new weak_ptr (public member function)
(destructor)	destroys a weak_ptr (public member function)
operator=	replaces the reference held in the weak_ptr (public member function)
Modifiers
reset	clears the reference held in the weak pointer (public member function)
swap	exchanges contents of two weak pointers (public member function)
Observers
use_count	returns the number of shared_ptrs that manage the object (public member function)
expired	checks if the referenced object exists (public member function)
lock	creates a shared_ptr that manages the referenced object (public member function)
owner_before	provides owner-based ordering of weak pointers (public member function)

[edit] Non-member functions

std::swap(std::weak_ptr) (C++11)	specializes the std::swap algorithm (function template)