[#BloombergLP-bdlb-ConstNullableValueRef-isNull]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlb.adoc[bdlb]::xref:BloombergLP/bdlb/ConstNullableValueRef.adoc[ConstNullableValueRef]::isNull
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:mrdocs:

Return `false` if the target contains a value, and `true` otherwise. Note that this accessor is provided purely for compatibility with `NullableValue` and `NullableAllocatedValue`, and its use is discouraged in favor of `has_value`.

== Synopsis

Declared in `<bdlb_nullablevalueref.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
bool
isNull() const noexcept;
----


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