yaml, activerecord and acts_as_nested_set

Geoffrey — Sun, 02 Dec 2007 16:41:00 +0100

I used to use this yaml_to_ar lib from christophe to load categories tree into my database, using acts_as_tree in the model that was perfect. Arrived the time when I felt the need to use acts_as_nested_set instead, for which I had to fill the lft and rgt columns. So I just rewrote the yaml_to_ar piece of code (put this in lib/yaml_to_ar.rb):

[ruby]
require 'yaml'

class YAML_to_AR

  def initialize(file, model)
    @data = File.open(file) { |yf| YAML::load( yf ) }
    @model = model
  end

  def process(data = @data, parent = nil)
    if data.is_a? Array
      data.each do |val|
        process(val, parent)
      end
    elsif data.is_a? Hash
      data.each do |key,val|
        parent = @model.create(:title => key)
        process(val, parent)
      end
    elsif data.is_a? String
      parent.add_child(@model.create(:title => data))
    end
  end

 end

This should handle both acts_as_tree and acts_as_nested. To ease things a bit further, I also wrote a rake task (to drop in lib/tasks/db_load_categories.rake for example):

[ruby]
namespace :db do
  desc "Loads categories defaults data"
  task :load_categories => :environment do
    require 'lib/yaml_to_ar'
    Category.delete_all
    categories = YAML_to_AR.new('db/categories.yml', Category)
    categories.process
  end
end

Now I just rake db:load_categories, and voila !

Mirmo Dynamics - Tag - rake

yaml, activerecord and acts_as_nested_set