使用Storyboard时出现以下警告：
warning: Unsupported Configuration: Scene is unreachable due to lack of entry points and does not have an identifier for runtime access via -instantiateViewControllerWithIdentifier:.
大意是为了在程序中动态访问Scene，需要给其设置一个Storyboard ID，所以给出了警告，解决方法：设置一个Storyboard ID即可
Scene is unreachable due to lack of entry points and does not have an identifier for runtime access
原文：http://www.cnblogs.com/code4app/p/4350852.html