From: Matthew Harris <shugotenshi@...>
Date: 2006-06-14T16:38:39+09:00
Subject: Re: impossible to sort a hash by key?

On 6/14/06, Oliver Katzer <ok@yum.de> wrote:
> Hi everyone!
>
> is it impossible to sort a hash by key?
>
> I have a hash like {"plums"=>3, "bananas"=>4, "apples"=>6}
>
> And what i want is {"apples" => 6, "bananas" => 4, "plums" => 3}
>
> Hash#sort returns an array. So i've tried this:
>
> class Hash
>  def sort_by_key
>    array = self.sort
>    # the array is sorted!
>    array.inject({}) do |hash, value|
>      hash[value.first] = value.last
>      hash
>    end
>  end
> end
>
> But the result is {"plums"=>3, "bananas"=>4, "apples"=>6}!
>
> So - is it impossible to sort a hash by key?
>
> Oliver.
>
> --
> Posted via http://www.ruby-forum.com/.
>
>

Hashes are unordered, an "ordered hash" is an oxymoron.
If you need a hash to be ordered, the easiest way is to use an array.

  irb(main):001:0> hsh = {:a => 1, :b => 2, :c => 3, :d => 4}
  => {:d=>4, :b=>2, :c=>3, :a=>1}
  irb(main):002:0> hsh.sort_by { |k,v| k }
  NoMethodError: undefined method `<=>' for :d:Symbol
          from (irb):2:in `sort_by'
          from (irb):2
          from :0
  irb(main):003:0> hsh.sort_by { |k,v| k.to_s }
  => [[:a, 1], [:b, 2], [:c, 3], [:d, 4]]

-- 
Matt