[#BloombergLP-bdlb-VariantImp-apply-028]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlb.adoc[bdlb]::xref:BloombergLP/bdlb/VariantImp.adoc[VariantImp]::apply
:relfileprefix: ../../../
:mrdocs:

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

== Synopsis

Declared in `<bdlb_variant.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class RET_TYPE,
    class VISITOR,
    class TYPE>
RET_TYPE
apply(
    VISITOR& visitor,
    TYPE const& defaultValue);
----

== Description

If this variant is unset, the specified `defaultValue` of template parameter `TYPE` is passed to the `visitor`. `TYPE` must be the same as one of the types that this variant can hold. The behavior is undefined unless this variant is unset or holds a value of template parameter `TYPE`.

== Return Value

result of invoking `visitor` on the active alternative

== Parameters

[cols="1,4"]
|===
| Name| Description
| *visitor*
| callable applied to the active alternative
| *defaultValue*
| value passed to `visitor` when this variant is unset
|===


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