class Greeting
  attr_accessor :who
end

class GreetingActor
  include Celluloid

  def initialize
    async.wait_for_msg
  end

  def wait_for_msg
    loop do
      receive { |msg|
        if msg.is_a? Greeting
          puts "Hello " + msg.who
        end
      }
    end
  end
end

greeter = GreetingActor.new
greeting = Greeting.new
greeting.who = "Dr Who"
greeter.mailbox << greeting