From: Jean-Hugues ROBERT <jean_hugues_robert@...>
Date: 2004-04-26T19:23:42+09:00
Subject: Re: How do you know it quacks like a duck? is there a list of  special methods?

At 06:44 26/04/2004 +0900, you wrote:
>Quoteing djd15@po.cwru.edu, on Tue, Apr 20, 2004 at 05:22:23AM +0900:
> > All the methods I can think of in the standard library that do different
> > things based on what they're passed, though, actually check the class of
> > the object (I think).
>
>I was reminded by this in a recent post, which said the ruby stdlib had
>been changed to use the presence of :read as a method to indicate an
>object is IO-like.  In that case, the categories I'm aware of are:
>
># Class     respond_to?
>   String     :to_str
>   Array      :to_ary
>   IO         :read
>   Symbol     :id2name (or is this silly? are only Symbols symbol-like?)
>
>Are there other "signature" methods?
>
>Would be useful on the wiki page, maybe under ruby-idioms?
>
>Cheers,
>Sam

I use some other ones in my code:
   xxx.respond_to? :each
   xxx.respond_to? :call
The first one is typically an Enumerable (an existing ruby module)
The second one is typically a Callable (Smalltalkish I think, nothing eqv 
in Ruby).

It may prove a good idea to encapsulate this in some methods (of Object)
class Object
   def stringable? ; respond_to? :to_str end
   def arrayable?  ; respond_to? :to_ary end
   def readable?   ; respond_to? :read   end
   def enumerable? ; respond_to? :each   end
   def callable?   ; respond_to? :call   end
end

But I suppose this is rather questionable?

Another option is to mixim the an appropriate module,
as is already the case for Enumerable.

Yours,

Jean-Hugues



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