http://ios.jobbole.com/93171/
http://blog.jobbole.com/79566/
http://www.cocoachina.com/bbs/read.php?tid=299721
https://www.objc.io/issues/4-core-data/
https://casatwy.com/iosying-yong-jia-gou-tan-wang-luo-ceng-she-ji-fang-an.html
https://github.com/skyming/Trip-to-IOS-Design-Patterns
https://cloud.tencent.com/community/tag/65/1?CKTAG=mta_share.tygsy
https://www.cnblogs.com/IT-Bear/p/5566506.html#tencent
http://gracelancy.com/blog/2013/08/11/make-your-own-cocoapods-spec/
http://gracelancy.com/blog/2012/12/15/cocoa-coding-guideline/
http://gracelancy.com/blog/2012/11/27/debug-objc-code/
http://www.tanhao.me/
http://tutuge.me/page/2/
http://tutuge.me/2014/11/01/%E7%AC%AC%E4%B8%80%E7%AF%87Blog/
https://github.com/joy0304/Joy-Blog/blob/master/iOSCollection.md
https://juejin.im/post/57ded1650bd1d00057f6da49
https://www.jianshu.com/p/be10e24d345f
https://juejin.im/post/58ca0832a22b9d006418fe43
http://www.jianshu.com/p/fba5d3e91bec
https://blog.ibireme.com/
https://github.com/southpeak/iOS-tech-set
https://note.youdao.com/share/?id=a4ab959d3fe22c4f4a1db4cf3726613f&type=note#/
https://www.jianshu.com/p/2f664e71c527
shift+control+command+4到剪切板
attribute((objc_subclassing_restricted))//一个不可被继承的类
假如想 box 一个 struct 类型或是 union 类型成 NSValue 对象，可以使用这个属性：
typedef struct attribute((objc_boxable)) {
CGFloat x, y, width, height;
} XXRect;
