#!/usr/bin/env rubyclass MegaGreeter  attr_accessor :names  # 初始化這個物件  def initialize(names = "World")    @names = names  end  # 向每個人說 hi  def say_hi    if @names.nil?      puts "..."    elsif @names.respond_to?("each")      # @names 是可以迭代的陣列容器      @names.each do |name|        puts "Hello #{name}!"      end    else      puts "Hello #{@names}!"    end  end  # 向每個人說 bye  def say_bye    if @names.nil?      puts "..."    elsif @names.respond_to?("join")      # 用逗號將陣列中的元素串接成一個字串      puts "Goodbye #{@names.join(", ")}.  Come back soon!"    else      puts "Goodbye #{@names}.  Come back soon!"    end  endendif __FILE__ == $0  mg = MegaGreeter.new  mg.say_hi  mg.say_bye  # 變更成 "Zeke"  mg.names = "Zeke"  mg.say_hi  mg.say_bye  # 變更成一個名字的陣列  mg.names = ["Albert", "Brenda", "Charles",    "Dave", "Engelbert"]  mg.say_hi  mg.say_bye  # 變更成 nil  mg.names = nil  mg.say_hi  mg.say_byeend