Where I show an iterative method of building an attr_reader type metaprogramming model

meta.rb

# Initial Rev
# machine.rb
class Machine
  def initialize(name)
    @name = name
  end

  def device
    Lot.find_by_tester(@name).device
  end
end

# 2nd Rev - Where we build a class method that will build 
#           an instance method.
# machine.rb
class Machine
  def initialize(name)
    @name = name
  end

  def self.associated_to(attr)
    class_eval %Q*
      def device
        Lot.find_by_#{attr}(@name).device
      end
    *
  end
  associated_to :tester
end

# 3rd Rev - where we move all the methods out to a module. 
#           Note the gymnastics we need to go through to build 
#           class methods in the module.
# machine.rb
class Machine
  include MakesAssociatedTo
  associated_to :tester
end

# makes_associated_to.rb
module MakesAssociatedTo
  def initialize(name)
    @name = name
  end

  def self.included(base)
    base.extend(ClassMethods)
  end

  module ClassMethods
    def associated_to(attr)
      class_eval %Q?
        def device
          Lot.find_by_#{attr}(@name).device
        end
      ?
    end
  end
end