Observer and Duck type

main.rb

$: << File.join(File.dirname(__FILE__), "/")

require "Observable.rb"
require "Observer1.rb"
require "Observer2.rb"

observable = Observable.new
o1 = Observer1.new(observable)
o2 = Observer2.new(observable)

observable.called

Observable.rb

class Observable
	def initialize
		@observers = []
	end

	def observe(o)
		@observers << o
	end

	def called
		puts "Observable is being called"
		@observers.each { |o| o.update }
	end
end

Observer1.rb

class Observer1
	def initialize(obs)
		obs.observe(self)
	end

	def update
		puts "Okay! Observing in Observer1"
	end
end

Observer2.rb

class Observer2
	def initialize(obs)
		obs.observe(self)
	end

	def update
		puts "Okay! Observing in Observer2"
	end
end