概述
今天在Xcode工程中遇到了如下问题：
This application is modifying the autolayout engine from a background thread after the engine was accessed from the main thread. This can lead to engine corruption and weird crashes.
原因分析
修改UILabel的text时不在主线程中。而UI控件的操作都必须在主线程下
解决方案
将UILabel的操作都放到主线程中即可
我是通过dispatch_get_main_queue来实现的
