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Can you pass a va_list as arguments to fill a CString (variable argument list)?

Posted on 1997-05-29
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Last Modified: 2013-12-03
I have a class member that accepts a string with formatting capability, and therefore can have multiple arguments to fill the format sections. Can I simply take the string I get and the argument list and send it to CString and let it do the work of stuffing? How can I do this. I want to take the formatted string and send it to an open I/O stream. I'm using MSVC++ 4.2 under Win95 and WinNT 4.x. (Must I just add my own function like the protected CString::FormatV)?)

Here's my function member:
/////////////////////////////////////////////////////////////////////////////////////////////////
// this function member will extract the arguments into a va_list, set the new string, and
// append the string to the open report file
// it will display an error if a file has not been opened first with OpenReportFile
// this function will allow the passing of arguments as used in the printf and
// CString::Format functions (see Microsoft VC++ help for information on formatting codes)
//
// Input Variables:  lpszformatstr - string of text to be written to open file w/formatting info
//                   ... - formatting variable argument list
//
// Output Variable: function status return (TRUE- success, FALSE- error)
BOOL KEMETReportClass::WriteLineToReportFile(LPCTSTR lpszformatstr, ...)
{
      // assure a good valid string
      ASSERT(AfxIsValidString(lpszformatstr,FALSE));

      // check that a file is actually open
      if (!FileOpened || reportfilehandle == NULL)
            {
            AfxMessageBox("KEMETReportClass Warning!\nNo File Has Been Opened.\nCannot Write Line.",MB_OK | MB_ICONEXCLAMATION);
            return(FALSE);
            }

      // stuff the text string into a formatted CString
      CString ReportLineTextString;
      va_list arglist;
      va_start(arglist,lpszformatstr);
      ReportLineTextString.Format("%s",lpszformatstr,arglist);
      va_end(arglist);

      // now check for empty string
      // if not empty, spit it to the file, othewise, display a NULL string error message
      if (!ReportLineTextString.IsEmpty())
            fprintf(reportfilehandle,"%s",ReportLineTextString);
      else
            {
            AfxMessageBox("KEMETReportClass Warning!\nCannot Write A NULL Text Line.",MB_OK | MB_ICONEXCLAMATION);
            return(FALSE);
            }
      
AfxMessageBox(ReportLineTextString);
      return(TRUE);
}
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Question by:maknight
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Accepted Solution

by:
jpk041897 earned 10 total points
ID: 1397711
valists separate strings from eachoter using nulls, for instance:

"String 1"\0"String 2"\0"String 3"\0\0

Deafault constructors for CString would only read the first string in the va list.

You would either have to derive a class from CString and add your own constructor or add a method that woud parse the va list and implement the functionality you desire.
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