From: elbows@... (Nathan Weston)
Date: 2004-06-06T11:38:40+09:00
Subject: Re: How to ducktype a Hash?

How about using the fetch and store methods? These work the same as
Hash#[] and Hash#[]=, but are unique to Hash.
Your other hash-like objects might not implement them, but they would
be easy to add.

Nathan

"Sean O'Dell" <sean@celsoft.com> wrote in message news:<200406041715.09691.sean@celsoft.com>...
> I need to detect when an object is a hash-like container for other objects, 
> one which responds to [] and which can index using any object as a value 
> (string, etc.).
> 
> My problem is, respond_to?(:[]) returns true for objects which are array-like 
> and for strings (both have [] methods).  I need to prevent strings, arrays, 
> and any other object which responds to :[] from getting to this one point in 
> code, and only allow a hash or hash-like object.  The data type at this 
> particular point in the code comes from a variety of data sources, and there 
> are lots of ways it could become a string, or an array or theoretically any 
> object.  I need to know when it's a hash or hash-like object, and raise an 
> exception when it is not.  My biggest problem right now is, when it's a 
> string or an array, the code has no way of knowing if the returned object/nil 
> is a valid value, or if a "undesirable" object has slipped in and returned 
> what it likes to return when you call its [] method.
> 
> So, how do I positively identify when an object is a hash or at least behaves 
> like a hash?
> 
> 	Sean O'Dell