gistfile1.rb

# event.rb
class Event < ActiveRecord::Base

 belongs_to :eventable, polymorphic: true

end

# migration
class CreateEvents < ActiveRecord::Migration
  def change
    create_table :events do |t|
      t.string :event_type
      t.integer :eventable_id
      t.string :eventable_type
      t.hstore :metadata
      t.timestamps
    end
  end
end


# eventable.rb
require 'active_support/concern'

module Eventable
  extend ActiveSupport::Concern

  EVENT_TYPES = [:accepted, :denied]

  included do
    has_many :events, as: :eventable
    attr_accessor :metadata
  end

  def create_event(type)
    Event.create(eventable: self, event_type: type, metadata: self.metadata)
  end

  # create dynamic methods based on the event types of the model
  #
  EVENT_TYPES.each do |event_type|
    define_method "create_#{event_type}_event" do |args={}|
      unless Hash(args).empty?
        if self.metadata.nil?
          self.metadata = args
        else
          self.metadata.merge(args)
        end
      end

      Event.create(eventable: self, event_type: event_type, metadata: self.metadata)
    end
  end



end