oc 面向协议

https://www.csdn.net/tags/MtTaAg1sNzI0ODQtYmxvZwO0O0OO0O0O.html

https://blog.csdn.net/zhangyutangde/article/details/78339123?utm_medium=distribute.pc_aggpage_search_result.none-task-blog-2~aggregatepage~first_rank_ecpm_v1~rank_v31_ecpm-3-78339123-null-null.pc_agg_new_rank&utm_term=ios+面向协议和面向对象&spm=1000.2123.3001.4430