From: Sean O'Dell <sean@...>
Date: 2004-06-06T14:24:06+09:00
Subject: Re: How to ducktype a Hash?

On Saturday 05 June 2004 21:36, Austin Ziegler wrote:
>
> IMO, Mr O'Dell needs to consider why he is checking for a
> "Hash-like" behaviour. As Nobu (?) suggested, this is more likely
> indicated by #each_pair than anything else (Struct behaves that way,
> although OpenStruct does not -- perhaps an oversight). After all,
> Procs implement #[] -- but they aren't Array *or* Hash (and this is
> because there is -- thankfully -- no () operator in Ruby).
>
> I see no problem with checking for #kind_of?(String), or Array, or
> Hash -- if you must absolutely have the semantics offered by those
> classes, since they are fundamental. However, doing so will limit
> your code rather severely, and there are alternatives in most cases.

I'm checking for hash-like behavior, because I have no control over the data 
coming in, and it gets converted to Ruby objectsprior to a certain point in  
code which expects these objects to be a hash-like object.  Right now, that 
can mean a hash, a custom class that has hash functionality, the Env object, 
or any other object that gets developed in the future with hash-like 
functionality.

kind_of?, respond_to? and simply duck typing don't help in this regard.  My 
only solution is to implement some sort of tagging method and tag Hash, the 
custom objects and any objects I can think of, and test for that.  That will 
work, but it feels like a kludge to run around tagging existing Ruby objects 
with a type id.

	Sean O'Dell