[#BloombergLP-bdlb-Variant_ReturnValueHelper]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlb.adoc[bdlb]::Variant&lowbar;ReturnValueHelper
:relfileprefix: ../../
:mrdocs:

This struct is a component&hyphen;private meta&hyphen;function&period; Do _not_ use&period; This meta&hyphen;function checks whether the template parameter type `VISITOR` has the member `ResultType` defined using &quot;SFINAE&quot; (Substitution Failure Is Not An Error)&period; A `value` of `true` indicates `VISITOR&colon;&colon;ResultType` exists, and `false` otherwise&period;

== Synopsis

Declared in `&lt;bdlb&lowbar;variant&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;class VISITOR&gt;
struct Variant&lowbar;ReturnValueHelper
    : xref:bsl/integral_constant-02.adoc[bsl::integral&lowbar;constant&lt;bool, sizeof (Variant&lowbar;ReturnValueHelper&lowbar;Matcher&colon;&colon;match&lt;VISITOR&gt;(0)) &equals;&equals; sizeof(Variant&lowbar;ReturnValueHelper&lowbar;YesType)&gt;]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:bsl/integral_constant-02.adoc[bsl::integral&lowbar;constant&lt;bool, sizeof (Variant&lowbar;ReturnValueHelper&lowbar;Matcher&colon;&colon;match&lt;VISITOR&gt;(0)) &equals;&equals; sizeof(Variant&lowbar;ReturnValueHelper&lowbar;YesType)&gt;]`
| Metafunction representing a compile&hyphen;time constant of the specified (template parameter) `t&lowbar;TYPE` with the specified (template parameter) `t&lowbar;VALUE`&period;
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:bsl/integral_constant-02/type.adoc[`type`] 
| Alias for this `integral&lowbar;constant` specialization&period;
| xref:bsl/integral_constant-02/value_type.adoc[`value&lowbar;type`] 
| 
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/integral_constant-02/operator_call.adoc[`operator()`] 
| Return a copy of the template argument `t&lowbar;VALUE`&period;
| xref:bsl/integral_constant-02/2conversion.adoc[`operator value&lowbar;type`] 
| 
|===


== Static Data Members

[cols="1"]
|===
| Name
| xref:bsl/integral_constant-02/value.adoc[`value`] 
|===



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