嵌套方法定义与调用

def toggle 
  def toggle 
    "subsequent times" 
  end 
  "first time" 
end

#irb
>>toggle # => "first time" 
>>toggle # => "subsequent times" 
>>toggle # => "subsequent times"

外围的toggle方法内定义了两个操作,一是对toggle方法的不同的定义,二是打印"first time",第一次调用toggle方法时,将执行这两个操作,结果是重定义toggle方法,然后打印"first time",所以以后再调用时,toggle方法定义已经改变,其行为是输出"subsequent times".