[Yaml-core] Re: [ANN] YAML.rb 0.49 -- new spec, new tokenizer

[Robert F. <fe...@ce...>]

On Wed, 8 Jan 2003, why the lucky stiff wrote:

> > Two things though, when I use Yaml for ini files I'd like to be able to
> > spec an order for map pairs to be serialized in. Obviously Ruby hashes has
> > no garantuee for this but are there any plans on supporting this? If not
> > I'll whip something up myself; I really wanna make sure the most important
> > stuff comes out on top...
>
> Was that two things?
>
Sorry it was very late. Not sure what the other thing was. I'll get back
to you if I remember... ;)

> Here's a few solutions to your dilemma:
>
>   2. The same can't be done for Hashes because the key set isn't
>      predictable.  But if the :SortKeys method is called, then
>      the Hash will be sorted with Hash#sort.  You could define a
>      singleton `sort' method to sort certain Hashes.
>
>       >> test = { 'name' => 'Alto Saxophone', 'key' => 'Eb',
>       >>          'is_woodwind' => true }
>       >> def test.sort
>       >>   order = [ 'name', 'key', 'is_woodwind' ]
>       >>   super { |a,b| order.index( a[0] ) <=> order.index( b[0] ) }
>       >> end
>       >>
>       >> puts test.to_yaml( :SortKeys => true )
>       name: Alto Saxophone
>       key: Eb
>       is_woodwind: true
>
>      Alternatively, you could define a singleton `to_a' to sort
>      correctly and skip the :SortKeys option.
>
That was what I ended up doing:

require 'yaml'

module SortableToAKeys
  def key_order=(keys)
    @__key_order = keys
  end

  def to_a
    ks, out = self.keys, []
    (@__key_order + (ks - @__key_order)).each do |key|
      out << [key, self[key]] if ks.include?(key)
    end
    out
  end
end

h = {1 => 1, 2=>2}
puts h.to_yaml + "\n----"

h.extend SortableToAKeys
h.key_order = [2, 1]
puts h.to_yaml

Thanks,

Robert