From: Robert Klemme <shortcutter@...>
Date: 2008-02-23T01:15:06+09:00
Subject: Re: ||= [] idiom

2008/2/22, Leslie Viljoen <leslieviljoen@gmail.com>:
> On Fri, Feb 22, 2008 at 2:33 PM, Thufir <hawat.thufir@gmail.com> wrote:
>  > On Wed, 20 Feb 2008 07:21:15 +0900, MenTaLguY wrote:
>  >
>  >  > I sometimes do this sort of thing:
>  >  >
>  >  >  ( @categories[resource.tag] ||= [] ) << resource
>  >  >
>  >  > Although this might possibly be more readable:
>  >  >
>  >  >  category = ( @categories[resource.tag] ||= [] ) category << resource
>  >  >
>  >  > Often it can make sense to factor the ||= portion into a separate
>  >  > method:
>  >  >
>  >  >  def category_for(tag)
>  >  >    @categories[tag] ||= []
>  >  >  end
>  >  >
>  >  >  # ...
>  >  >
>  >  >    category_for(resource.tag) << resource
>  >  >
>  >  > -mental
>  >
>  >  What's the real-world application of this?
>
> It's for making hashes of arrays:

I may be wrong here but I read Thufir's question differently: it seems
he is asking for the application of refactoring this into a separate
method.

Kind regards

robert

-- 
use.inject do |as, often| as.you_can - without end