From: Lex Williams <etaern@...>
Date: 2008-10-02T03:23:31+09:00
Subject: Re: Ordered hash hack for < ruby 1.9?

Ben Johnson wrote:
> Patrick Doyle wrote:
>> Why not iterate over myhash.keys.sort instead of just myhash.keys?
>> 
>> --wpd
> 
> Because for performance it's bad. I don't care if performance is bad in 
> my tests. Which is why it would be nice to alter how hashes work ONLY in 
> my test environment. But sorting by keys isn't smart either.
> 
>>> a = {:a => 1, :b => 2}
> => {:a=>1, :b=>2}
>>> a.keys.sort
> NoMethodError: undefined method `<=>' for :a:Symbol
>   from (irb):16:in `sort'
>   from (irb):16
>   from :0

Here's a hack for altering the original Hash class :

class Hash
  alias :old_equals :[]=
  attr_reader :ordered_values

  def []=(key,value)
    @ordered_values ||= []
    @ordered_values << key
    old_equals(key,value)
  end


end

hsh = {}
hsh["a"]="b"
hsh["b"]="c"
hsh.ordered_values.each do |key|
  puts key
end

###
outputs a,b
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