From: Ryan Leavengood <mrcode@...>
Date: 2005-06-27T04:34:43+09:00
Subject: Re: grouping/sorting [newbie question]

bdarcus@gmail.com wrote:
>
> E.g. it only creates a new "group" if one doesn't already exist?  Was
> wondering how to do that, so thanks for this!

That is one way. Hashes can also take a block in their constructors 
which can be used for default values:

h = Hash.new {|h,k| h[k] = 'default'}
h['foo'] = 'bar'
p h['foo']   # => "bar"
p h['baz']   # => "default"

For the code I wrote before, it would be like this:

grouped_comments = films.inject(Hash.new {|h,k| h[k] = []}) do |grouped, 
film|
   grouped[film['title']] << film['comments']
   grouped
end

But in this case I prefer the ||= syntax.

Ryan