Ruby – 实例方法：为什么我可以在没有self的情况下使用getter,

class Game

  attr_accessor :in_progress

  def initialize
    @in_progress = false
  end

  def start!

    # debug info                                                                         
    puts self.inspect                        # => #<Game:0x8f616f4 @in_progress=false>
    puts self.class.instance_methods(false)  # => [:in_progress,:in_progress=,:start!]
    puts self.instance_variables             # => [:@in_progress]
    puts self.respond_to?("in_progress=")    # => true

    puts in_progress      # => true - getter works without self
    # main quesion
    in_progress = true    # Why setter doesn't work without self?

    # self.in_progress = true   # this would work and set @in_progress to true becase setter called
    # @in_progress = true       # this would work as well because we set instance variable to true directly

  end

end

g = Game.new
g.start!
puts g.in_progress # => false - setter in start! method didn't work

我们在这里有什么：

>使用@in_progress变量的getter和setter的类游戏
>默认情况下,@ in_progress为false
>我们打电话开始！方法并尝试将in_progress更改为true
> in_progress的Getter效果很好
> Setter只适用于自己.或通过@in_progress直接访问变量

我读到了Ruby中的方法查找(向右移动一步到接收器的类中,然后向上移动祖先链,直到找到方法.)
但我真的不知道为什么我必须使用self.in_progress = true来访问setter方法.特别是当getter方法无需自我时.

提前致谢！