From: Ryan Leavengood <leavengood@...>
Date: 2005-11-23T07:33:21+09:00
Subject: Re: what is the ruby way to do this?

On 11/22/05, ako... <akonsu@gmail.com> wrote:
> hello,
>
> i am still learning. in the below code @attributes is a hash table. i
> want to add a new value 'a' for a key represented by 'a.key'. i also
> want to group values with the same keys in to arrays. thanks for any
> help.
>
> konstantin
>
> if @attributes.has_key?(a.key)
>   if @attributes[a.key].is_a?(Array)
>     @attributes[a.key] << a
>   else
>     @attributes[a.key] = [@attributes[a.key], a]
>   end
> else
>   @attributes[a.key] = a
> end

This is a fairly standard Ruby idiom (a hash of arrays):

(@attributes[a.key]||=[])<<a

What the above is doing is setting the entry for a.key to an empty
array if nothing exists, otherwise it will return the array already at
that location. Then the element a is added to that array.

Ryan