changing the ordering of taxons based on yaml

categories-sample.yml

---
- 
  Wine & Spirits:
    -
      Beer: []
    -
      Wine:
      - Red
      - White
      - Blush
      - Champagne
      - Sparkling
    -
      Spirits:
      - Whisky
      - Rum
      - Vodka
      - Tequila/Gin
      - Liqueur
      - Cognac/Brandy
      - Other Spirits
    -
      Non-Alcoholic: []

taxon_position.rake

    desc "set up the ordering of taxons using config/categories.yml as a blueprint"
    task :position_taxons => :environment do
      TaxonPositioneer.new.go
    end

taxon_positioneer.rb

class TaxonPositioneer
  attr_reader :taxon_tree # this is for debugging purposes
  
  def initialize
    @taxon_tree = YAML::load File.open(RAILS_ROOT + "/config/categories.yml")
  end
  
  def go
    pos = 1
    @taxon_tree.each do |taxonomy|
      # now we have a hash with one key
      taxonomy.each do |t,v|
        puts "  * In #{t} assiging position #{pos}:"
        parent = Taxon.find_by_name(t)
        parent.position = pos
        parent.save
        pos = pos + 1

        "#{v.length} second level taxons"
        v.each do |kk|
          kk.each do |kkey, vv|
            puts " ** Processing the #{kkey} second level assigning position #{pos}"
            second = Taxon.find(:first, :conditions => ["name = ?", kkey])
            next if second.nil?
            second.position = pos
            second.save
            pos = pos + 1
          
            puts "#{vv.length} third level taxons"
            #third level
            vv.each do |vvv|
              puts "*** doing #{vvv} third level assigning position #{pos}"
              third = Taxon.find_by_name(vvv)
              next if third.nil?
              puts third.class
              third.position = pos
              third.save
              pos = pos + 1
            end
          end
        end
      end
    end
  end
  
end

the reason the categories-sample is full of arrays, is that arrays allow easy enforcement of ordering.