From: Ron Jeffries <ronjeffries@...>
Date: 2002-02-14T02:14:41+09:00
Subject: Re: qualms about respond_to? idiom

On Wed, 13 Feb 2002 16:28:59 GMT, David Alan Black
<dblack@candle.superlink.net> wrote:

>OK -- but does this suggestion mean that you would see the
>"responds_to?" idiom as a sign that something's wrong with the code?
>Actually, this all started for me with my work on NQXML::Dispatcher,
>when I was originally branching on type:
>
>  if e.is_a? NQXML::Tag
>    if e.startTag?
>      ...
>
>
>and got enlightened on IRC about not branching on type or depending on
>type in Ruby :-)  So I've learned to think of branching-on-type as a
>sign that something needs to be fixed; now I'm wondering whether the
>responds_to? idiom should be viewed similarly (rather than as an
>acceptable rewrite of branching on type).

Yes. I think that use of "responds_to?" is in general a fairly intense
code smell.

Ronald E Jeffries
http://www.XProgramming.com
http://www.objectmentor.com
I'm giving the best advice I have. You get to decide whether it's true for you.