Re: Homework question relating to docview

From:

"Doug Harrison [MVP]" <dsh@mvps.org>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 13 Jul 2007 00:17:00 -0500

Message-ID:

<nn1e9357kotpa66mogmcc8m7c2uojce7jt@4ax.com>

On Fri, 13 Jul 2007 04:28:23 GMT, "David Ching" <dc@remove-this.dcsoft.com>
wrote:

I thought so too, but CDocument defines

virtual BOOL OnOpenDocument(LPCTSTR lpszPathName);
virtual BOOL OnSaveDocument(LPCTSTR lpszPathName);

which are overrides and not message handlers, so I don't think these qualify
for CCmdTarget-ness?

-- David

"Message handler" and "virtual" aren't mutually exclusive. That said, those
functions aren't message handlers but are instead called from various
message handlers as part of the open/save procedures. A major problem with
normal (non-virtual) message handlers is getting polymorphic behavior out
of them; you have to use SendMessage or PostMessage, which is clumsy and
error-prone. Functions that are intended to be overridden and called from
many places are best expressed as virtual functions, which of course can be
called from message handlers. If you want to find the actual message
handlers, search for ID_FILE_SAVE and ID_FILE_OPEN. You'll find the UI is
done outside of the CDocument functions you quoted, which are essentially
the customizable, non-UI guts of the open/save procedures.

--
Doug Harrison
Visual C++ MVP