摘要：
Recently I am working on migrate an old and complex project to ARC, I have learned some knowledges about ARC and reprinted some useful topics before, but I still have some barriers. After I solve these issues, I decide to write it down as a record. Not every tip is written by myself, some tips are from internet. Although I have the same problems as others, but I think their language description is better than me. If I find any new tips about ARC I will update to this article. 阅读全文
