From: Tim Bates <tim@...>
Date: 2003-08-09T08:48:10+09:00
Subject: Re: Ducktype, right?

On Sat, Aug 09, 2003 at 06:46:26AM +0900, Dave Thomas wrote:
> In general, if a Ruby programmer finds themselves using respond_to? too 
> much, I'd ask them 'why?'.
> 
> If they're switching on the result, then I'd recommend looking at 
> polymorphic solutions, or possibly double dispatch.
> 
> If they're checking parameters, I'd suggest commenting out the check and 
> seeing what happens.  :)

This is something like my approach to Duck Typing. The documentation of
my library says that this method parameter expects a Duck *or similar*.
The actual code does no checking of whether it's a Duck or a Giraffe, or
even if it can quack; it just asks it to quack. If I'm feeling
particularly zealous, I even document what methods of Duck I actually
use. Then, it's up to the user of my library: if they pass in a Goose,
and it can quack, good for them. If they pass in a Mouse, they can
expect things to break. It's probably not the most robust of coding
styles, but I write my libraries for intelligent people (ie me), not to
be foolproof. Of course, I perform lots of sanity checking on my
end-user input. ;)

Tim Bates
-- 
tim@bates.id.au