[#BloombergLP-bdlat-NullableValueUtil-accessValueByCategory]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlat.adoc[bdlat]::xref:BloombergLP/bdlat/NullableValueUtil.adoc[NullableValueUtil]::accessValueByCategory
:relfileprefix: ../../../
:mrdocs:

Invoke a categorized accessor on the value held by a nullable object.

== Synopsis

Declared in `<bdlat_nullablevalueutil.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class TYPE,
    class ACCESSOR>
static
int
accessValueByCategory(
    TYPE const& object,
    ACCESSOR& accessor);
----

== Description

Invoke the specified `accessor` on the non‐modifiable value stored in the specified "nullable" `object` and on a prvalue of the category tag type for the dynamic category of the value. See {`bdlat_typecategory`|Category Tags and Enumerators} for documentation about category tags. Return the value from the invocation of `accessor`. The `accessor` must be an accessor functor. See {`bdlat_typecategory`|`ACCESSOR` Functors} for the requirements on `accessor`. The behavior is undefined if `object` contains a null value.

== Return Value

value from the invocation of `accessor`

== Parameters

[cols="1,4"]
|===
| Name| Description
| *object*
| "nullable" object whose held value is accessed
| *accessor*
| functor applied to the held value with a category tag
|===


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