observer.rb

#!/bin/env ruby

# encoding: utf-8

require 'observer'

class CriminalMovement  include Observable  attr_reader :criminal  def initialize(criminal)    @criminal = criminal  end  def action(msg)    changed    notify_observers(criminal, msg)  endendclass Criminal  attr_reader :name  def initialize(name)    @name = name  endendclass FbiMovement  attr_reader :fbi  def initialize(fbi)    @fbi = fbi  end  def update(criminal, msg)    p criminal.name + msg + ': ' + fbi.name + '收到'  endendclass Fbi  attr_reader :name  def initialize(name)    @name = name  endend# 卧底class Dinting  def self.run    crmn1 =  Criminal.new('黑狗')    crmn2 =  Criminal.new('黑虎')    fbi1 = Fbi.new('飞鹰1号')    fbi2 = Fbi.new('飞鹰2号')    fbi1_observer = FbiMovement.new(fbi1)    fbi2_observer = FbiMovement.new(fbi2)    crinimal1_observer = CriminalMovement.new(crmn1)    crinimal2_observer = CriminalMovement.new(crmn2)    fbi_observers = [fbi1_observer, fbi2_observer]    crinimal_observers = [crinimal1_observer, crinimal2_observer]    fbi_observers.each do |fbi_o|      crinimal_observers.each do |cri_o|        cri_o.add_observer(fbi_o)      end    end    crinimal1_observer.action('今天凌晨2点，南河小巷抢劫')    crinimal2_observer.action('明天凌晨2点，爱河毒品交易')  endendDinting.run

程序运行结果：

"黑狗今天凌晨2点，南河小巷抢劫: 飞鹰1号收到"

"黑狗今天凌晨2点，南河小巷抢劫: 飞鹰2号收到"

"黑虎明天凌晨2点，爱河毒品交易: 飞鹰1号收到"

"黑虎明天凌晨2点，爱河毒品交易: 飞鹰2号收到"