Re: Static class member error

From:
"Doug Harrison [MVP]" <dsh@mvps.org>
Newsgroups:
microsoft.public.vc.mfc
Date:
Wed, 07 May 2008 21:19:14 -0500
Message-ID:
<57o424p9s1tn0il3p94toja145ua3htm1p@4ax.com>
On Wed, 7 May 2008 19:56:29 -0400, "Jeov? Almeida" <jeovaalmeida@yahoo.com>
wrote:

Hello Doug,

You said

The second parameter must be a const reference or simply a CString,
because it's illegal to bind a temporary to a non-const reference.


The second parameter is an output parameter, that is, if some error occurs
during the processing I can get the error message and log it, if I want. If
I make it a const reference, when I assign a value the strErrorMsg, I get
the error:

C2678: binary '=' : no operator found which takes a left-hand operand of
type 'const CString' (or there is no acceptable


Right, you can't assign to an object through a const reference, unless the
class is very, very weird and defines a const operator=.

I didn't realize it was an out parameter. What I said about binding a
temporary to a non-const reference is correct, and you shouldn't use a
default argument here. (Please ignore the fact that it works. <g> Try
compiling with /Za and you'll find that it doesn't.) It would be better to
stop using the default argument and split the function into two functions,
e.g.

static CString Get(LPCTSTR strURL)
{
   CString x;
   return Get(strURL, x);
}

static CString Get(LPCTSTR strURL, CString& strErrorMsg);

How do you distinguish an error return from a non-error return? If you
throw an exception, you can include an error message in the exception
object, and then you won't need the strErrorMsg parameter.

--
Doug Harrison
Visual C++ MVP

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