From -7969063946549420597 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,8c9f1307b83ac2db X-Google-Attributes: gidf78e5,public From: Valentin Bonnard Subject: Re: Q: virtual functions not overridable anymore? Date: 1997/09/26 Message-ID: <34293558.73F@pratique.fr>#1/1 X-Deja-AN: 275854261 References: <01bcb109$1e790180$433574cf@worldnet.worldnet.att.net> <3404A0AE.6F7E@Eng.Sun.COM> <5uimip$l56@bgtnsc03.worldnet.att.net> <340D93AA.643A@Eng.Sun.COM> <01bcb951$ea80a440$909c389d@mtayler> <34166C9E.1882@pratique.fr> <341E7C8E.EA4@pratique.fr> <3420858D.12DB@mWilden.com> X-Original-Date: Wed, 24 Sep 1997 17:44:25 +0200 Organization: Internet Way X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBVAwUBNCw5U0y4NqrwXLNJAQGeQAIAjDVnH76baMczoNVdbO9VAzvlLfT739di unBy7FSiRvCYFBkVZauntEaeriMm891E0qGNSwpMfyv7gtz9LoF1ZQ== =x4kz Reply-To: bonnardv@pratique.fr Newsgroups: comp.std.c++ Originator: austern@isolde.mti.sgi.com Mark Wilden writes: > Valentin Bonnard wrote: > > > > Let's say you have the following GUI classes: > > > > class Window { > > virtual void draw () = 0; > > }; > > > > class Dialog { > > void draw () > > { > > for_each (items.begin (), items.end (), > > ptr_mem_fun (DialogItem::draw)); > > } > > list items; > > }; [...] > > You might want to declare Dialog::draw () final as at this point, > > behaviour should be changed by deriving from DialogItem, not Dialog. > > That would prevent you from doing something like this: > > struct DebugDialog : Dialog { > void draw() > { > cout << "About to draw dialog" << endl; > Dialog::draw(); > cout << "Done drawing dialog" << endl; > } > }; But any non-virtual function prevents you from doing that. virtual functions aren't a way to patch program to remove bugs or to introduce debugging tests; they are a way to write OO programs where the derived class define a function the correct way. Your argument is against non-virtual functions (thus all non-members functions), not against final. Remember: the original argument was: since we have non-virtual functions, we should have final functions (ie non-virtual functions overiding from virtual functions). -- Valentin Bonnard mailto:bonnardv@pratique.fr info about C++/a propos du C++: http://www.pratique.fr/~bonnardv/ --- [ comp.std.c++ is moderated. To submit articles: Try just posting with your newsreader. If that fails, use mailto:std-c++@ncar.ucar.edu comp.std.c++ FAQ: http://reality.sgi.com/austern/std-c++/faq.html Moderation policy: http://reality.sgi.com/austern/std-c++/policy.html Comments? mailto:std-c++-request@ncar.ucar.edu ]