https://www.jianshu.com/p/b74e52e866fc
https://www.jianshu.com/p/9cf65105364d
https://blog.csdn.net/wzc10101415/article/details/80306728
https://blog.csdn.net/mydo/article/details/52808579
http://www.cocoachina.com/ios/20170810/20207.html
分类目录归档：iOS
iOS开发者申请发布证书及真机调试 图文详解
https://blog.csdn.net/xx326664162/article/details/48087709
iOS多线程下单例
http://www.dreamingwish.com/article/gcd-guide-dispatch-once-1.html
iOS多线程开发
https://blog.csdn.net/shenjie12345678/article/details/44152605