[#bsl-weak_ptr-0d]
= xref:bsl.adoc[bsl]::weak_ptr
:relfileprefix: ../
:mrdocs:

This `friend` declaration provides access to the internal data members while constructing a weak pointer from a weak pointer of a different type.

== Synopsis

Declared in `<bslstl_sharedptr.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class ELEMENT_TYPE>
class weak_ptr;
----

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:bsl/weak_ptr-0d/element_type.adoc[`element_type`] 
| Alias to the element type referenced by this `weak_ptr`.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/weak_ptr-0d/2constructor-03.adoc[`weak_ptr`]         [.small]#[constructor]#
| Constructors
| xref:bsl/weak_ptr-0d/2destructor.adoc[`~weak_ptr`] [.small]#[destructor]#
| Destroy this weak pointer object. If this weak pointer manages a (possibly shared) object, release the weak reference to that object.
| xref:bsl/weak_ptr-0d/operator_assign-09.adoc[`operator=`] 
| Assignment operators
| xref:bsl/weak_ptr-0d/acquireSharedPtr.adoc[`acquireSharedPtr`] 
| Return a `shared_ptr` to the observed object, or empty if expired.
| xref:bsl/weak_ptr-0d/expired.adoc[`expired`] 
| Return `true` if this weak pointer is in the empty state or the object that it originally referenced has been destroyed, and `false` otherwise.
| xref:bsl/weak_ptr-0d/lock.adoc[`lock`] 
| Return a shared pointer to the object referred to by this weak pointer if `false == expired()`, and a shared pointer in the empty state otherwise.
| xref:bsl/weak_ptr-0d/numReferences.adoc[`numReferences`] 
| Return the number of `shared_ptr` owners of the observed object.
| xref:bsl/weak_ptr-0d/owner_before-00.adoc[`owner_before`] 
| Return whether this `weak_ptr` precedes `other` in owner order.
| xref:bsl/weak_ptr-0d/owner_equal-02.adoc[`owner_equal`] 
| Return whether this pointer shares ownership with `other`.
| xref:bsl/weak_ptr-0d/owner_hash.adoc[`owner_hash`] 
| Return a hash value based on this pointer's ownership identity.
| xref:bsl/weak_ptr-0d/rep.adoc[`rep`] 
| Return the address of the held representation, or null if empty.
| xref:bsl/weak_ptr-0d/reset.adoc[`reset`] 
| Reset this `weak_ptr` to the empty state.
| xref:bsl/weak_ptr-0d/swap.adoc[`swap`] 
| Exchange the state of this `weak_ptr` with `other`.
| xref:bsl/weak_ptr-0d/use_count.adoc[`use_count`] 
| Return the number of `shared_ptr` owners of the observed object.
| xref:bsl/weak_ptr-0d/2conversion.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<weak_ptr<ELEMENT_TYPE>, is_nothrow_move_constructible>`] 
| Nested trait declaration for `is_nothrow_move_constructible`.
|===


== Deduction Guides

[cols="1,4"]
|===
| Name| Description
| xref:bsl/weak_ptr-07.adoc[`weak_ptr<ELEMENT_TYPE>`] 
| Deduce the specified type `ELEMENT_TYPE` corresponding template parameter of the `bsl::shared_ptr` supplied to the constructor of `weak_ptr`.
|===


== Friends

[cols="1,4"]
|===
| Name| Description
| `bsl::weak_ptr`
| This `friend` declaration provides access to the internal data members while constructing a weak pointer from a weak pointer of a different type.
|===

== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/swap-0447.adoc[`swap`]
| Exchange the states of the specified `weak_ptr` objects `a` and `b`.
|===


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