Ultra simple state for models.

can_have_state.rb

module CanHaveState
  def can_have_state(states = {})
    class_eval do
      const_set("STATES", states.freeze)
      const_set("STATE_CODE_TO_NAME", self::STATES.invert.freeze)

      states.each do |type, value|
        # Create some helper methods and scopes
        scope type, where(:state => value)

        define_method "#{ type.to_s }?" do
          self.state == value
        end

        define_method type.to_s do
          self.state = value
        end
      end

      def self.states
        self::STATES.keys
      end

      def self.state_code(name)
        name = name.to_sym
        raise ArgumentError, "#{name} not a valid state" unless self::STATES.has_key?(name)
        self::STATES[name]
      end
      
      def self.state_name(code)
        raise ArgumentError, "#{code} not a valid state" unless self::STATES.has_value?(code)
        self::STATE_CODE_TO_NAME[code].to_s
      end
    end
  end
end