Re: dynamic_cast

From	Bonita Montero <Bonita.Montero@gmail.com>
Newsgroups	comp.lang.c++
Subject	Re: dynamic_cast
Date	2021-07-03 17:01 +0200
Organization	A noiseless patient Spider
Message-ID	<sbpu3o$pkd$1@dont-email.me> (permalink)
References	(2 earlier) <sbl7mh$kb5$1@dont-email.me> <sbpm58$tfv$1@dont-email.me> <oMZDI.15364$SA.31@fx39.iad> <sbpq4k$ql6$1@dont-email.me> <j3_DI.7823$en4.873@fx34.iad>

Show all headers | View raw

>> If you're doing a dynamic_cast you're switching upon the type of the
>> class. This switching should be better done inside the class with class
>> -dependent code - with a virtual function call.

> Wrong. Application level logic should stay in the application level
> code. That is the only scalable option.

Virtual function calls are more scalable.

>>> As an example, say you have a collection of animals, and you want to
>>> extract all the dogs out of it. You could add to Animal and Dog an isDog
>>> function, (and then need to change Animal again for each new type of
>>> thing you might want get, lousy encapsulation) or you can use a
>>> dynamic_cast to check if this animal is a Dog.

>> the isDog-function would be faster.

> But then  it also needs isCat, isHorse, isSnake, isMammel, isReptile,
> and so on.

Maybe, but that's much faster. Dynamic downcasts are slower.

> The virtual function method says that you need to change Animal EVERY
> TIME you define a new type of animal for the system. This breaks
> encapsulation, ...

No, it is encapsulation.

Thread

dynamic_cast Mr Flibble <flibble@reddwarf.jmc> - 2021-06-27 22:51 +0100
  Re: dynamic_cast Öö Tiib <ootiib@hot.ee> - 2021-06-27 15:01 -0700
  Re: dynamic_cast Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-06-27 22:30 +0000
  Re: dynamic_cast "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-06-27 16:35 -0700
  Re: dynamic_cast Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-28 08:44 +0200
    Re: dynamic_cast Vir Campestris <vir.campestris@invalid.invalid> - 2021-07-01 21:14 +0100
      Re: dynamic_cast Öö Tiib <ootiib@hot.ee> - 2021-07-01 14:16 -0700
      Re: dynamic_cast red floyd <no.spam.here@its.invalid> - 2021-07-01 17:48 -0700
      Re: dynamic_cast Bonita Montero <Bonita.Montero@gmail.com> - 2021-07-03 14:45 +0200
        Re: dynamic_cast Richard Damon <Richard@Damon-Family.org> - 2021-07-03 09:39 -0400
          Re: dynamic_cast Bonita Montero <Bonita.Montero@gmail.com> - 2021-07-03 15:53 +0200
            Re: dynamic_cast Richard Damon <Richard@Damon-Family.org> - 2021-07-03 09:59 -0400
              Re: dynamic_cast Bonita Montero <Bonita.Montero@gmail.com> - 2021-07-03 17:01 +0200
                Re: dynamic_cast Richard Damon <Richard@Damon-Family.org> - 2021-07-03 11:42 -0400
                Re: dynamic_cast Bonita Montero <Bonita.Montero@gmail.com> - 2021-07-03 18:04 +0200
                Re: dynamic_cast Richard Damon <Richard@Damon-Family.org> - 2021-07-03 13:59 -0400
                Re: dynamic_cast Mr Flibble <flibble@reddwarf.jmc> - 2021-07-03 20:06 +0100
                Re: dynamic_cast Bonita Montero <Bonita.Montero@gmail.com> - 2021-07-04 07:06 +0200
                Re: dynamic_cast Richard Damon <Richard@Damon-Family.org> - 2021-07-03 14:03 -0400
                Re: dynamic_cast Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-08-07 13:06 -0700

csiph-web