内隐创造的帮助者-路线。rb和“匹配”的语句

I am reading Obie Fernandez' "The Rails 3 Way", and there is a bit of it that I am not sure I understand correctly. I am new to rails, and want to make sure I understand it correctly. I have some experience with vanilla Ruby. Not much, but some.I am reading Obie Fernandez' "The Rails 3 Way",