From: Phrogz <gavin@...>
Date: 2007-01-21T03:15:06+09:00
Subject: Re: Proper way to either create or append to an array?

Robert Klemme wrote:
> Since you're using a Hash the block constructor is the most elegant
> solution IMHO:
>
> def initialize
>    @foo = Hash.new {|h,k| h[k]=[]}
>    ...
> end

To be clear for those unfamiliar with this: any time you ask for the
value of a key that doesn't exist, the block will be called (which
creates a new empty array). This means you can never see this
particular Hash has a key, since:
  if @foo[ :bar ]
will always succeed, and create a (possibly unwanted) array instance in
the process.