From: why the lucky stiff <ruby-talk@...>
Date: 2005-05-15T06:44:50+09:00
Subject: Re: how to keep hash sort from YAML

dave wrote:

>how can I cast a YAML hash data into a ruby obj without
>any auto-sort feature?
>---
>2: 1
>1: 2
>3: 3
>  
>
James is correct.  Neither Ruby nor YAML allows hashes to be ordered.  
However, Ruby's YAML library includes an Omap type[1], which acts like 
the ordered dictionaries you'll find in PHP.

A basic demonstration:

  >> require 'yaml'
  => true
  >> omap = YAML::Omap['c', 1, 'a', 2, 'b', 3]
  => [["c", 1], ["a", 2], ["b", 3]]
  >> y omap
  --- !omap
  - c: 1
  - a: 2
  - b: 3

As you can see, the Omap is just an array that contains hash pairs.  You 
can use the Omap in Ruby just like a Hash.

  >> omap2 = YAML::load( YAML::dump( omap ) )
  => [["c", 1], ["a", 2], ["b", 3]]
  >> omap2.each { |k,v| p [k,v] }
  ["c", 1]
  ["a", 2]
  ["b", 3]

_why
[1] http://yaml.org/type/omap.html