publisher.rb

module Publisher                                                                    
  def self.included(base)                                                           
    base.instance_eval do                                                           
      def republish(*messages)                                                      
        messages.each do |message|                                                  
          define_method(message) do |args|                                          
            publish(message, *args)                                                 
          end                                                                       
        end                                                                         
      end                                                                           
    end                                                                             
  end                                                                               
  
  def add_subscriber(subscriber)                                                    
    @subscribers ||= []                                                             
    @subscribers << subscriber                                                      
  end                                                                               
  
  def add_subscribers(subscribers)                                                  
    subscribers.each { |subscriber| add_subscriber(subscriber) }                    
  end                                                                               
  
  def publish(message, *args)                                                       
    return if @subscribers.blank?                                                                                                                                             
    @subscribers.each do |subscriber|                                               
      subscriber.send(message, *args) if subscriber.respond_to?(message)            
    end                                                                             
  end                                                                               
end