From: Joel VanderWerf <vjoel@...>
Date: 2008-02-20T07:23:54+09:00
Subject: Re: ||= [] idiom

Sebastian Hungerecker wrote:
> Leslie Viljoen wrote:
>> @categories = {}
>>
>> pagelist.each do |resource|
>>     @categories[resource.tag] ||= []
>>     @categories[resource.tag] << resource
>> end
>>
>>
>> .. is there a better way?
> 
> @categories = Hash.new {Array.new}
> pagelist.each do |resource|
>   @categories[resource.tag] << resource
> end

That one still bites me from time to time...

irb(main):001:0> h = Hash.new {Array.new}
=> {}
irb(main):002:0> h[4]
=> []
irb(main):003:0> h[4] << 5
=> [5]
irb(main):004:0> h
=> {}


Try this...

irb(main):005:0> h = Hash.new {|h,k| h[k]=Array.new}
=> {}
irb(main):006:0> h[4] << 5
=> [5]
irb(main):007:0> h
=> {4=>[5]}

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407