observable_array.rb

require 'observable'

class ObservableArray
  include Observable
  
  def initialize(array = [])
    @array = array
  end
  
  protected
  
  def method_missing(method, *args, &block)
    if @array.respond_to?(method)
      current_hash = @array.hash
      @array.send(method, *args, &block)
      notify_changes if @array.hash != current_hash
    else
      super
    end
  end
  
  private
  
  def notify_changes
    changed(true) and notify_observers(self)
  end
end

# class MyObserver
#   def update(array)
#     puts "Array #{array} has changed"
#   end
# end
# 
# a = ObservableArray.new
# o = MyObserver.new
# a.add_observer(o)