Re: _variant_t

From:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>

Newsgroups:

microsoft.public.vc.mfc,microsoft.public.vc.language

Date:

Thu, 27 Mar 2008 16:43:33 -0400

Message-ID:

<tf6dnfPwkpZqm3HanZ2dnUVZ_vOlnZ2d@comcast.com>

"Eric Kaplan" <tobycraftse@yahoo.com> wrote in message
news:550ou3h01v9movmnk8i85kkjmjk0661kea@4ax.com...

Why I got error for following code:
vtValue == VT_NULL

1>d:\trash4\database\database.cpp(156) : error C2593: 'operator ==' is
ambiguous

======================
bool Table::Get(char* FieldName,int& FieldValue){

_variant_t vtValue;
vtValue = m_Rec->Fields->GetItem(FieldName)->GetValue();
if (vtValue == VT_NULL ){
FieldValue = 0;
} else {
FieldValue=vtValue.date;
}

}

(comp.lang.c++ trimmed)

_variant_t is a class that wraps a struct that wraps a union. In other
words it has many parts. You are attempting to compare something that has
many parts to some constant number. Seems meaningless to me.

Then again, the documentation for _variant_t says it overloads operator ==
to compare two _variant_t objects. But that is not what you are asking it
to compare.

I think you need to find out which member of the _variant_t you expect a
VT_NULL result in and compare that member to VT_NULL.

--
Scott McPhillips [VC++ MVP]