?
Solved

How to extract a string from a cOleVariant

Posted on 1998-12-03
4
Medium Priority
?
964 Views
Last Modified: 2013-11-20
Hello,

I'm kind of new to MFC so this might be quite an easy question for some, but I haven't been able to find the answer anywhere.  

I'm writing an application that uses DAO to access an indexed database and read the contents of a field. This is the procedure I'm following:
(1) set the index
(2) call the seek method
(3) If matches are found, get a particular field from the matching record.

Now, I know that that field will give me a string, but the GetField method of the DaoRecordset class returns a cOleVariant variable with the information inside.  I desperately need to extract the string out of the cOleVariant object but don't know how.  Please help if you can.

Thanks.
0
Comment
Question by:pizarro
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
4 Comments
 
LVL 2

Expert Comment

by:wyy_cq
ID: 1325744
COleVariant::operator LPCVARIANT
returns a VARIANT structure .

VARIANT is a structure with a flag and a union.
in the union many type variable. bstrVal is a string.
but when you access it, you 'd better check the flag first.

when you get the VARIANT you can do like this to get the string.
CString s;
s=pVAR->bstrVal;
0
 

Author Comment

by:pizarro
ID: 1325745
I tried what you said and I don't get an error any longer.  However,  I keep getting a "?" for something I know is a string, which means, somehow the string is not being taken out of the COleVariant object correctly.  This is the code I'm using:

void CFiltroImagenExtension::EnviarBandera(CHttpServerContext* pCtxt,
                                        LPTSTR usuario, LPTSTR banner)
{
    int iFound;
      COleVariant oPais;
      CString sPais;
      const VARIANT *vPais;
      COleVariant oIndexField;
      CDaoDatabase dbBannerManager;
      CDaoRecordset dbUsuarios(&dbBannerManager);
   
      oIndexField=COleVariant(usuario,VT_BSTRT);

      dbBannerManager.Open("c:\\BannerManager.mdb", false, true);
              dbUsuarios.Open(dbOpenTable, "Usuarios");
   
      dbUsuarios.SetCurrentIndex("Usuario");
      iFound=dbUsuarios.Seek("=", &oIndexField);
   
      StartContent(pCtxt);
      WriteTitle(pCtxt);

      if( iFound > 0 ){
            //Return Info
            oPais=dbUsuarios.GetFieldValue("pais");
            vPais= LPCVARIANT(oPais);
            sPais = vPais->bstrVal;  //Instead of getting a string for sPais,
                                                                //I'm always getting the "?" sign.
      }else{
            //Return failed Info
            //Do something else
      }

}

Instead of getting a comprehensible string for sPais (Which I know what it is in anticipation) I get a question mark "?".
0
 
LVL 6

Accepted Solution

by:
snoegler earned 800 total points
ID: 1325746
sPais = V_BSTRT(&oPais);

This is like it is done in the class CCrack, which is part of the
MSVC documentation. Just browse the help for 'CCrack', then
you'll see how the MSVC programmers did it.
0
 

Author Comment

by:pizarro
ID: 1325747
Just how I like it... Nice and easy :) Thanks.
0

Featured Post

Moving data to the cloud? Find out if you’re ready

Before moving to the cloud, it is important to carefully define your db needs, plan for the migration & understand prod. environment. This wp explains how to define what you need from a cloud provider, plan for the migration & what putting a cloud solution into practice entails.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This is to be the first in a series of articles demonstrating the development of a complete windows based application using the MFC classes.  I’ll try to keep each article focused on one (or a couple) of the tasks that one may meet.   Introductio…
Introduction: Ownerdraw of the grid button.  A singleton class implentation and usage. Continuing from the fifth article about sudoku.   Open the project in visual studio. Go to the class view – CGridButton should be visible as a class.  R…
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
In this video, Percona Director of Solution Engineering Jon Tobin discusses the function and features of Percona Server for MongoDB. How Percona can help Percona can help you determine if Percona Server for MongoDB is the right solution for …

762 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question