[#BloombergLP-bslstl-Variant_VTableId-05]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::Variant_VTableId
:relfileprefix: ../../
:mrdocs:

This component‐private struct computes an array in which element `i` is a pointer to `Variant_FunctionId<t_RET, t_VISITOR, t_VARIANT, i>::functionImpl`, defined above as a function that invokes a `t_VISITOR` with a tag representing `i` and alternative `i` of `t_VARIANT`, implicitly converting the return type to `t_RET`. Implementation note: The constexpr static maps of pointers defined by `Variant_VTable` and this class have deliberately been defined in two different classes as having them in the same class caused issues with Clang and Microsoft Visual C++.

== Synopsis

Declared in `<bslstl_variant.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_RET,
    class t_VISITOR,
    class t_VARIANT,
    class t_DUMMY>
struct Variant_VTableId;
----

== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslstl/Variant_VTableId-01.adoc[`Variant_VTableId<t_RET, t_VISITOR, t_VARIANT, bslmf::IntegerSequence<std::size_t, t_INDICES...>>`] 
| In order to allow for perfect forwarding, both t_VISITOR and t_VARIANT must be of reference type. If they are not, something went wrong.
|===



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