forwarding variable number of arguments

[mistretzu]

I want to write a general method that will add entries to a log file.
My problem is that i don't know how to pass all the arguments from logEvent() method to CString::Format()

void CXServerLogFile::logEvent( UINT resID, char *first, ... )
{
CString strEvent;
strEvent.Format( resID, .... ); // what do i put here?
strEvent += "\n";
writeEvent( strEvent );
}

[mistretzu]

I made some debuging through MFC to see how CString::Format() works, and i found the answer to my problem. Here is the code:

void CXServerLogFile::logEvent( UINT resID, ... )
{
CString strEvent;
CString strFormat;
strFormat.LoadString( resID );

va_list argList;
va_start( argList, resID );
strEvent.FormatV( strFormat, argList );
va_end( argList );

strEvent += "\n";
writeEvent( strEvent );
}

[Graham]

Using va_args is very unsafe (you lose all your type-checking and parameter validation by the compiler). You would probably be better off looking for a solution that uses function overloading, rather than this extremely ugly method.

[galathaea]

If all of the arguments are of the same type, I've always felt that this article by the Saint of the New Form () worked fairly well. Otherwise, for different types, one should look into a type safe hetrogeneous container like a vector of boost::any, as found at www.boost.org and just pass one argument of this form...