Recordsets: converting COleVariant

[TrimTrom]

Hello,

VC++6.0 Prof, Win98

I am a new VC++ programmer looking for help.

I am trying to open a recordset on the fly and read a value from the first record. This apparently
necessitates using GetFieldValue with a COleVariant variable. My code is as follows:-

CDaoDatabase* pDB = new CDaoDatabase;
try
{
pDB->Open("D:\\Vb4&5prg\\Experiment\\Mail1.mdb");
}
catch(CDaoException* e)
{
AfxMessageBox(e->m_pErrorInfo->m_strDescription, MB_ICONEXCLAMATION);
e->Delete();
}

CDaoRecordset pRS(pDB);
CString mText = "Select * from Folders";
try
{
pRS.Open(AFX_DAO_USE_DEFAULT_TYPE, mText,0);
}
catch(CDaoException* e)
{
AfxMessageBox(e->m_pErrorInfo->m_strDescription, MB_ICONEXCLAMATION);
e->Delete();
}
pRS.MoveFirst();
COleVariant mVar;
int i = 1;
mVar = pRS.GetFieldValue(i);
mText = mVar;
AfxMessageBox(mText);
pDB->Close();
delete pDB;



The above fails on the attempt to pass the COleVariant value into a CString. I would be grateful for code
examples on how to convert a COleVariant into something that can be readily used, preferably a CString.
If there are any other errors in my code, I'd also be glad to know.

Hoping for help from all you experts,

TrimTrom

----------------------------------
Email: paul.trimming_nospam@dial.pipex.com
Surrey, England
----------------------------------

[chiuyan]

I have never done anything like you are doing, but to get a COleVariant into a CString, assuming that it has a valid BSTR in it, all you need to do is:

CString MyString = MyOleVariant.bstrVal;

--michael

[acj]

You will need a function, that is not defined in MFC to convert COleVariant to CString.
This function is defined in the follow lines:

//This function is necessary to strVARIANT work
LPCTSTR strBOOL(BOOL bFlag)
{
return bFlag ? _T("TRUE") : _T("FALSE");
}


//You must insert the prototype in the headers
CString strVARIANT(const COleVariant& var)
{
CString strRet;
strRet = _T("Fish");
switch(var.vt){
case VT_EMPTY:
case VT_NULL:
strRet = _T("NULL");
break;
case VT_I2:
strRet.Format(_T("%hd"),V_I2(&var));
break;
case VT_I4:
strRet.Format(_T("%d"),V_I4(&var));
break;
case VT_R4:
strRet.Format(_T("%e"),(double)V_R4(&var));
break;
case VT_R8:
strRet.Format(_T("%e"),V_R8(&var));
break;
case VT_CY:
strRet = COleCurrency(var).Format();
break;
case VT_DATE:
strRet = COleDateTime(var).Format(_T("%m %d %y"));
break;
case VT_BSTR:
strRet = V_BSTRT(&var);
break;
case VT_DISPATCH:
strRet = _T("VT_DISPATCH");
break;
case VT_ERROR:
strRet = _T("VT_ERROR");
break;
case VT_BOOL:
return strBOOL(V_BOOL(&var));
case VT_VARIANT:
strRet = _T("VT_VARIANT");
break;
case VT_UNKNOWN:
strRet = _T("VT_UNKNOWN");
break;
case VT_I1:
strRet = _T("VT_I1");
break;
case VT_UI1:
strRet.Format(_T("0x%02hX"),(unsigned short)V_UI1(&var));
break;
case VT_UI2:
strRet = _T("VT_UI2");
break;
case VT_UI4:
strRet = _T("VT_UI4");
break;
case VT_I8:
strRet = _T("VT_I8");
break;
case VT_UI8:
strRet = _T("VT_UI8");
break;
case VT_INT:
strRet = _T("VT_INT");
break;
case VT_UINT:
strRet = _T("VT_UINT");
break;
case VT_VOID:
strRet = _T("VT_VOID");
break;
case VT_HRESULT:
strRet = _T("VT_HRESULT");
break;
case VT_PTR:
strRet = _T("VT_PTR");
break;
case VT_SAFEARRAY:
strRet = _T("VT_SAFEARRAY");
break;
case VT_CARRAY:
strRet = _T("VT_CARRAY");
break;
case VT_USERDEFINED:
strRet = _T("VT_USERDEFINED");
break;
case VT_LPSTR:
strRet = _T("VT_LPSTR");
break;
case VT_LPWSTR:
strRet = _T("VT_LPWSTR");
break;
case VT_FILETIME:
strRet = _T("VT_FILETIME");
break;
case VT_BLOB:
strRet = _T("VT_BLOB");
break;
case VT_STREAM:
strRet = _T("VT_STREAM");
break;
case VT_STORAGE:
strRet = _T("VT_STORAGE");
break;
case VT_STREAMED_OBJECT:
strRet = _T("VT_STREAMED_OBJECT");
break;
case VT_STORED_OBJECT:
strRet = _T("VT_STORED_OBJECT");
break;
case VT_BLOB_OBJECT:
strRet = _T("VT_BLOB_OBJECT");
break;
case VT_CF:
strRet = _T("VT_CF");
break;
case VT_CLSID:
strRet = _T("VT_CLSID");
break;
}
WORD vt = var.vt;
if(vt & VT_ARRAY){
vt = vt & ~VT_ARRAY;
strRet = _T("Array of ");
}
if(vt & VT_BYREF){
vt = vt & ~VT_BYREF;
strRet += _T("Pointer to ");
}
if(vt != var.vt){
switch(vt){
case VT_EMPTY:
strRet += _T("VT_EMPTY");
break;
case VT_NULL:
strRet += _T("VT_NULL");
break;
case VT_I2:
strRet += _T("VT_I2");
break;
case VT_I4:
strRet += _T("VT_I4");
break;
case VT_R4:
strRet += _T("VT_R4");
break;
case VT_R8:
strRet += _T("VT_R8");
break;
case VT_CY:
strRet += _T("VT_CY");
break;
case VT_DATE:
strRet += _T("VT_DATE");
break;
case VT_BSTR:
strRet += _T("VT_BSTR");
break;
case VT_DISPATCH:
strRet += _T("VT_DISPATCH");
break;
case VT_ERROR:
strRet += _T("VT_ERROR");
break;
case VT_BOOL:
strRet += _T("VT_BOOL");
break;
case VT_VARIANT:
strRet += _T("VT_VARIANT");
break;
case VT_UNKNOWN:
strRet += _T("VT_UNKNOWN");
break;
case VT_I1:
strRet += _T("VT_I1");
break;
case VT_UI1:
strRet += _T("VT_UI1");
break;
case VT_UI2:
strRet += _T("VT_UI2");
break;
case VT_UI4:
strRet += _T("VT_UI4");
break;
case VT_I8:
strRet += _T("VT_I8");
break;
case VT_UI8:
strRet += _T("VT_UI8");
break;
case VT_INT:
strRet += _T("VT_INT");
break;
case VT_UINT:
strRet += _T("VT_UINT");
break;
case VT_VOID:
strRet += _T("VT_VOID");
break;
case VT_HRESULT:
strRet += _T("VT_HRESULT");
break;
case VT_PTR:
strRet += _T("VT_PTR");
break;
case VT_SAFEARRAY:
strRet += _T("VT_SAFEARRAY");
break;
case VT_CARRAY:
strRet += _T("VT_CARRAY");
break;
case VT_USERDEFINED:
strRet += _T("VT_USERDEFINED");
break;
case VT_LPSTR:
strRet += _T("VT_LPSTR");
break;
case VT_LPWSTR:
strRet += _T("VT_LPWSTR");
break;
case VT_FILETIME:
strRet += _T("VT_FILETIME");
break;
case VT_BLOB:
strRet += _T("VT_BLOB");
break;
case VT_STREAM:
strRet += _T("VT_STREAM");
break;
case VT_STORAGE:
strRet += _T("VT_STORAGE");
break;
case VT_STREAMED_OBJECT:
strRet += _T("VT_STREAMED_OBJECT");
break;
case VT_STORED_OBJECT:
strRet += _T("VT_STORED_OBJECT");
break;
case VT_BLOB_OBJECT:
strRet += _T("VT_BLOB_OBJECT");
break;
case VT_CF:
strRet += _T("VT_CF");
break;
case VT_CLSID:
strRet += _T("VT_CLSID");
break;
}
}
return strRet;
}


Example:

CString varstring;
COleVariant varole;
varole = tb.GetFieldValue("Field_Name");
varstring = strVARIANT(varole);

[TrimTrom]

Brilliant - it seems to be a very comprehensive function!

Thanks,

TrimTrom

----------------------------------
Email: paul.trimming_nospam@dial.pipex.com
Surrey, England
----------------------------------

[pva]

I noticed your post this last Tues, but didn't get a chance to respond. The sample code on your post doesn't include "endcatch" to both "try/catch" exception traps. I made this mistake once, and got an error. Check your actual code and see if you omitted "endcatch".

[nordyj]

This method only works some of the time for me (don't really know why), but I've never had a problem with using the V_BSTRT macro:CString MyString=V_BSTRT(&MyOleVariant);