From: E S <eero.saynatkari@...>
Date: 2005-01-14T03:34:03+09:00
Subject: Re: Duck Typing as Pattern Matching

> L�hett�j�: "trans.  (T. Onoma)" <transami@runbox.com>
> Aihe: Re: Duck Typing as Pattern Matching
> 
> I haven't read the entire thread so forgive me if I'm rehashing....
> 
> On Thursday 13 January 2005 09:51 am, itsme213 wrote:
> | "ts" <decoux@moulon.inra.fr> wrote in message
> |
> | > p txn.respond_to?(:create_modify)
> | > p txn.create_modify
> |
> | Oh oh, even more Ruby experts join the chorus ? :-)
> |
> | My claim is this: If you redefine #method_missing so your object handles
> | x.foo as the caller would expect, then you _should_ define
> | x.respond_to?(:foo) to return true. I do not claim that Ruby should
> | prohibit code that does not do this.
> 
> I wonder if method missing would be better if these two "tiers" were built in 
> to it. This would require dual "blocks" so I'm not sure how to notate it but:
> 
>   def method_missing(meth, *args)
>   upon meth == :create_modify
>     # do whatever
>   upon ...
>     # ...
>   end
> 
> Then #respond_to? can utilize the "upon" block to determine responses 
> correctly.

Are you thinking something different than

def method_missing(meth, *args)
  case meth
    when :create_modify
      # ...
  end
end

?


> | I am interested in your thoughts on this claim.
> |
> | p.s. I know it is possible to redefine #send so that x.send :foo works, but
> | x.foo does not. I think this a practice to be actively discouraged. But
> | let's leave that out for now.
> 
> Redefining #send is a very bad idea. IMHO That's one of those methods I think 
> should be off limits and return an error if you try to redefine it.
> 
> T.

E