From: Jeff Mitchell <quixoticsycophant@...>
Date: 2004-06-06T17:10:57+09:00
Subject: Re: How to ducktype a Hash?


--- Sean O'Dell <sean@celsoft.com> wrote:
> On Saturday 05 June 2004 15:01, John W. Long wrote:
> > >why do you need to say 'it is hash like' ?
> > >Wo'nt it be easyer to say 'I need this methods, so I'll just check
> > >them' ?
> > >
> > >BTW, probably the simpler solution is :
> > >
> > >x.methods =={}.methods
> >
> > This is even worse than object.kind_of(Hash). The whole point of "duck
> > typing" (as I understand it) is that you don't check if an object has
> > certain methods. You just use them. Ruby will throw an error if there's
> > a problem.
> 
> Which always sounded fine to me until I was actually exposed to this kind of 
> "typing."  The problem is, the methods [] and []= are there, they just don't 
> do what I need them to do.  Duck typing completely and utterly don't help, 
> and Ruby has no way to tell me when an object's [] and []= are hash-like or 
> something else.  My solution is going to end being something like "tagging 
> all objects that I know in advance to be hash-like, and then looking for that 
> tag at that particular point in my code."  That's a kludge to me.

Why should you expect [] to imply hash-like behavior in the first place?  It's
just a convenience method.  What was the problem with the #lookup and #store
suggestion at [ruby-talk:102505]?

Honestly I don't see the issue here.  The criteria you've chosen for a duck
is: "makes a light sound while walking".  Well, tons of animals do that.
You need distinct "QUACK"s.  Those quacks are #store and #lookup.



	
		
__________________________________
Do you Yahoo!?
Friends.  Fun.  Try the all-new Yahoo! Messenger.
http://messenger.yahoo.com/