标签：blank 文章 target www logs blog log ref pat
观察者模式好文章
https://blog.csdn.net/crave_shy/article/details/21235855
https://www.cnblogs.com/smyhvae/p/3899208.html
https://www.cnblogs.com/zuoxiaolong/p/pattern7.html
https://www.jianshu.com/p/3459188bc8f9
标签：blank 文章 target www logs blog log ref pat
原文地址：https://www.cnblogs.com/hunter-zyg/p/9246392.html
