BloombergLP::bdlb::Variant_ReturnValueHelper

Synopsis

Declared in <bdlb_variant.h>

template<class VISITOR>
struct Variant_ReturnValueHelper
    : bsl::integral_constant<bool, sizeof (Variant_ReturnValueHelper_Matcher::match<VISITOR>(0)) == sizeof(Variant_ReturnValueHelper_YesType)>

Description

Do not use. This meta-function checks whether the template parameter type VISITOR has the member ResultType defined using "SFINAE" (Substitution Failure Is Not An Error). A value of true indicates VISITOR::ResultType exists, and false otherwise.

Base Classes

Name	Description
`bsl::integral_constant<bool, sizeof (Variant_ReturnValueHelper_Matcher::match<VISITOR>(0)) == sizeof(Variant_ReturnValueHelper_YesType)>`	Metafunction representing a compile-time constant of the specified (template parameter) `t_TYPE` with the specified (template parameter) `t_VALUE`.

Type Aliases

Name	Description
`type`	Alias for this `integral_constant` specialization.
`value_type`	Alias for the (template parameter) `t_TYPE`.

Member Functions

Name	Description
`operator()`	Return a copy of the template argument `t_VALUE`.
`operator t_TYPE`	Return a copy of the template argument `t_VALUE`.

Static Data Members

Name	Description
`value`	The compile-time constant value of this metafunction.