https://blog.toright.com/posts/617/from-oop-to-aop-%e5%be%9e%e7%89%a9%e4%bb%b6%e5%b0%8e%e5%90%91%e5%88%b0%e6%96%b9%e9%9d%a2%e5%b0%8e%e5%90%91%e7%a8%8b%e5%bc%8f%e8%a8%ad%e8%a8%88