Tag ActiveRecord models

Taggable.rb

module Taggable

  def self.included(base)
    base.send :include, InstanceMethods
    base.extend ClassMethods
  end
  
  module ClassMethods
    def initialize(collection_names)
      delimiter = ','
      collection_names.map(&:to_s).each do |collection_name|
        owner_name = self.name.downcase
        class_name = collection_name.to_s.classify
        method_name = collection_name.to_s.singularize
        has_many_name = [owner_name, collection_name].sort
        has_many_name = [has_many_name.first.singularize, has_many_name.last.pluralize].join('_').to_sym

        class_eval do
          before_save :"set_#{collection_name}"
          has_many has_many_name, :dependent => :destroy
          has_many collection_name, :through => has_many_name
        end

        code = %(
          def #{method_name}_list
            @#{method_name}_list ||= self.#{collection_name}.collect(&:name)
            @#{method_name}_list.join('#{delimiter} ')
          end

          def #{method_name}_list=(#{method_name}_names)
            return if #{method_name}_names.blank?
            @#{method_name}_list = #{method_name}_names.split('#{delimiter}').collect(&:strip).uniq.reject(&:blank?)
            @#{method_name}_list
          end

          def set_#{collection_name}
            return if @#{method_name}_list.nil?

            existing = self.#{collection_name}.map(&:name)

            self.#{collection_name} = []

            @#{method_name}_list.each do |#{method_name}_name|
              self.#{collection_name} << #{class_name}.find_or_create_by_name(#{method_name}_name)
            end
          end
        )
        class_eval code
      end
    end

    def taggable(*args)
      initialize(args)
    end
    
  end

  module InstanceMethods
  end
end