Rails lookup v3 - String accessors for the lookup type

gistfile1.rb

   def lookup(as_name)
     #...

     #Now, define the foreign key from Car to CarType.
     belongs_to lookup_name.to_s.to_sym, :foreign_key => "#{as_name}".to_sym
     validates "#{as_name.to_s}_id".to_sym, :presence => true

      #Now we define the "delegates" that will allow us to just set call car.car_type = "Sports"
      #Define a setter for car_type
      define_method("#{as_name.to_s}_id=") do |id|
        #We would have used instance_variable_get. However rails maintains a hash of attributes 
        #that we must use to play nicely along with rails. Here we write the ID of the value
        #instead of the value itself inside the field.
        write_attribute "#{as_name.to_s}".to_sym, id
      end

      # Setter via String
      define_method("#{as_name.to_s}=") do |val|
        id = cls.gen_id_for val
        write_attribute "#{as_name.to_s}".to_sym, id
      end

      # Getter for the ID
      define_method("#{as_name.to_s}_id") do 
        read_attribute "#{as_name.to_s}".to_sym
      end

      #Define the getter
      define_method("#{as_name.to_s}") do 
        id = read_attribute "#{as_name.to_s}".to_sym
        if not id.nil?
          value = cls.name_for id
          if value.nil?
            # This is reached in case many processes use the DB and some other process
            # inserted a new value that we were not aware of, but who's ID was inserted
            # into this object.
            lookup_obj = cls.find_by_id id
            if not lookup_obj.nil?
              cls.name_for id, lookup_obj.name
              cls.id_for lookup_obj.name, id             
            end
          end
        end
        value
      end

    #...
  end