设计模式
https://waleon.blog.csdn.net/article/details/66974516?spm=1001.2101.3001.6661.1&utm_medium=distribute.pc_relevant_t0.none-task-blog-2%7Edefault%7ECTRLIST%7EPayColumn-1.pc_relevant_default&depth_1-utm_source=distribute.pc_relevant_t0.none-task-blog-2%7Edefault%7ECTRLIST%7EPayColumn-1.pc_relevant_default&utm_relevant_index=1