1.x和2.x之间Rails的变化哪些实际影响了你在Rails中的工作？

I'm doing a course on Rails that focuses on version 1.1.6 so I'm trying to figure out which of the numerous changes between 1.x and 2.x are the most critical to be aware of for practical use. At the moment I don't need to know all the little nitty gritty changes - just the big ones.I'm doing a course on Rails that focuses on ver