A Public::Activity concern which allows you to create custom activities when arbitrary triggers occur.

eventable.rb

# PublicActivity Concern to allow custom activities to be created when certain triggers occur.
#
# Usage Example:
#
# class Challenge < ActiveRecord::Base
#   include Eventable
#   eventable :after_save => [{
#     key: 'challenge.after_publish',
#     when: "self.public_changed? && self.public?",
#     recipients: 'self.potential_members'
#   },
#   {
#     key: 'challenge.winners_chosen',
#     when: "self.status_id_changed? && self.status == 'Winners Chosen'",
#     recipients: 'self.entrants'
#   },
#   {
#     key: 'challenge.closed',
#     when: "self.status_id_changed? && self.status == 'Closed'",
#     recipients: 'self.potential_members'
#   }]

module Eventable
  extend ActiveSupport::Concern

  module ClassMethods
    def eventable(*arr)
      arr.each do |options|
        options.keys.each do |kallback|
          define_method "eventable_#{kallback}" do
            self.instance_variable_set("@_#{kallback}_hooks", options[kallback])
          end
          self.send(kallback, proc { self.send(:process_events_for, self.send("eventable_#{kallback}"))})
        end
      end
    end
  end

  included do
    include PublicActivity::Common
  end

  def process_events_for(arr)
    arr.each do |a|
      if a[:when].nil? || eval(a[:when])
        (eval(a[:recipients]) || []).each do |recipient|
          self.create_activity key: a[:key], owner: self, recipient: recipient, parameters: a[:parameters] || {}
        end
      end
    end
  end
end