From: William James <w_a_x_man@...>
Date: 2005-11-05T11:52:09+09:00
Subject: Re: How does one sort hash of hashes by multiple values?

joe.yakich@gmail.com wrote:
> Imagine I have this data structure:
>
>      @my_hash[8858]['name'] = 'goober'
>      @my_hash[8858]['sort_date'] = 19991231
>
>      @my_hash[2004]['name'] = 'goober'
>      @my_hash[2004]['sort_date'] = '20010416'
>
>      @my_hash[8872]['name'] = 'pyle'
>      @my_hash[8872]['sort_date'] = '20010416'
>
>      @my_hash[89]['name'] = 'hogan'
>      @my_hash[89]['sort_date'] = '2004 0918'
>
>      @my_hash[9]['name'] = 'homer'
>      @my_hash[9]['sort_date'] = '19980718'
>
> How does one sort it first by the name value, then by the sort_date
> value? (So that the name == 'goober' items appear before the others,
> and the very first element returned by the sort would be
> @my_hash[8858]?)
>
> I tried searching a bit (the FAQ and google) , but came up empty; sorry
> if this is a noob question. (Although, I am a ruby noob, so...)
>
> TIA!
>
> Joe

require 'pp'

my_hash = Hash.new { |hash, key| hash[key] = Hash.new }

     my_hash[8858]['name'] = 'goober'
     my_hash[8858]['sort_date'] = '19991231'

     my_hash[2004]['name'] = 'goober'
     my_hash[2004]['sort_date'] = '20010416'

     my_hash[8872]['name'] = 'pyle'
     my_hash[8872]['sort_date'] = '20010416'

     my_hash[89]['name'] = 'hogan'
     my_hash[89]['sort_date'] = '20040918'

     my_hash[9]['name'] = 'homer'
     my_hash[9]['sort_date'] = '19980718'

pp my_hash.sort_by{|x|  [ x.last['name'], x.last['sort_date'] ] }

---------------------------->

[[8858, {"name"=>"goober", "sort_date"=>"19991231"}],
 [2004, {"name"=>"goober", "sort_date"=>"20010416"}],
 [89, {"name"=>"hogan", "sort_date"=>"20040918"}],
 [9, {"name"=>"homer", "sort_date"=>"19980718"}],
 [8872, {"name"=>"pyle", "sort_date"=>"20010416"}]]