From: William James <w_a_x_man@...>
Date: 2008-02-20T07:30:19+09:00
Subject: Re: ||= [] idiom

On Feb 19, 4:11 pm, Leslie Viljoen <leslievilj...@gmail.com> wrote:
> I often make use of this idiom to add something to an array in a hash of arrays:
>
> @categories = {}
>
> pagelist.each do |resource|
>     @categories[resource.tag] ||= []
>     @categories[resource.tag] << resource
> end
>
> . is there a better way? Can the two @categories lines
> be made into one?
>
> Les

irb(main):001:0> h = Hash.new { |hash, key| hash[key] =[] }
=> {}
irb(main):002:0> h['foo'] << 33
=> [33]
irb(main):003:0> h['foo'] << 44
=> [33, 44]
irb(main):004:0> h
=> {"foo"=>[33, 44]}