state_machine_example.rb

module SamyRoad
  module FeedsEntryStatus
    extend ActiveSupport::Concern

    STATES = {
        ignored: 1,
        pending: 0,
        published: 2,
        erased: 3
    }

    included do

      STATES.each_pair do |state, value|
        scope state, where(status: value)
      end

      state_machine :status, :initial => :pending do
        after_transition any - :pending => :pending, do: :set_as_pending
        after_transition :pending => any - :pending, do: :unset_as_pending

        STATES.each_pair do |s, value|
          state s, value: value
        end

        event :publish do
          transition  [:pending, :ignored, :erased] => :published
        end

        event :ignore do
          transition :pending => :ignored
        end

        event :pending do
          transition :ignored => :pending
        end

        event :erase do
          transition  :published => :erased
        end
      end

    end

    module ClassMethods
      def states
        SamyRoad::FeedsEntryStatus::STATES.keys
      end
    end

    def set_as_pending
      notify_observers(:after_set_as_pending)
    end

    def unset_as_pending
      notify_observers(:after_unset_as_pending)
    end

  end
end