Ruby stateable lib for ActiveRecord class

stateable.rb

# Author: Diego d'Ursel
# ---------------------
#
# This simple lib help you to add state to a model without implementing boring functions for each state
# just add macro like "add_state 1, 'mystate'" to the definition of your ActiveRecord model
# this lib require a "state" field in the model
# 
# some example of usage:
# ---------------------
# add_state 0, 'inactive'
# add_state 1, 'active'
# add_state 3, 'deleted'
# 
# instance.inactive? => true/false
# instance.active! => update_attribute(...)
# instance.active => 1
# 
# instance.state => 3
# instance.state_to_s => 'deleted'
# Model.state_active.all

module Stateable

  states = {} # need flat scope

  # add accessor that return a string
  define_method :state_to_s do 
    states[self.state]
  end

  ClassMethods = Module.new do
      
    define_method :add_state do |num, str|
      # init variables 
      states[num] = str

      # add my_state?
      define_method "#{str}?" do
        self.state == states.key(str)
      end

      # add modifier my_state!
      define_method "#{str}!" do
        self.update_attribute(:state, states.key(str))
      end

      # return the number behind the string
      # this could be moved to a class method instead of instance
      define_method "#{str}" do
        states.key(str)
      end

      # add scope state_mystate
      self.scope "state_#{str}".to_sym, where("#{self.table_name}.state = ?", states.key(str))
    end    
  end
  
  def self.included(receiver)
    receiver.extend ClassMethods
  end
end