From: James Edward Gray II <james@...>
Date: 2007-03-02T07:30:37+09:00
Subject: Re: Duck Typing  Hash-Like Objects

On Mar 1, 2007, at 4:25 PM, Gary Wright wrote:

> I often find that when writing initialize (or alternate constructors)
> I want to examine the class of the arguments to decide how to
> proceed.  An example is Array.new, which behaves differently if it
> is given an integer argument or an array argument:
>
>    Array.new 2      # [nil,nil]
>    Array.new [1,2]  # [1,2]
>
> These sorts of tests can be done via Class#=== or Kernel#is_a? or
> Kernel#kind_of? but that can lead to artificial constraints.  Using
> Kernel#respond_to? seems to avoid many of those constraints.
>
> My question is:  What is the least constraining test to determine
> if you've got a hash-like object?  Is arg.respond_to?(:has_key?)
> reasonable?

I would check for to_hash(), then call that method on the argument to  
get its Hash representation.

James Edward Gray II