[#BloombergLP-bdlb-VariantImp-apply-034]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlb.adoc[bdlb]::xref:BloombergLP/bdlb/VariantImp.adoc[VariantImp]::apply
:relfileprefix: ../../../
:mrdocs:

Apply `visitor` to the held value of this modifiable variant.

== Synopsis

Declared in `<bdlb_variant.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class VISITOR>
VISITOR::ResultType
apply(VISITOR const& visitor)
requires Variant_ReturnValueHelper<VISITOR>::value == 1;
----

== Description

If If this variant is unset, a default constructed `bslmf::Nil` is passed to the `visitor`. Note that this method is selected only if the template parameter type `VISITOR` defines a `typedef` of `ResultType` in its public interface. Also note that this method is defined inline to work around a Windows compiler bug with SFINAE functions.

== Return Value

result of invoking `visitor` on the active alternative

== Parameters

[cols="1,4"]
|===
| Name| Description
| *visitor*
| callable applied to the active alternative
|===


[.small]#Created with https://www.mrdocs.com[MrDocs]#