Failed to instantiate the default view controller for UIMainStoryboardFile 'Main' - perhaps the designated entry point is not set? 错误分析。

在ios开发过程中，经常需要删除Main.storyboard重新拖控件生成Main.storyboard。这时候往往容易忘记勾选is Initial View Controller选项，导致了xcode没有了默认的启动界面，就会报错，错误代码

Failed to instantiate the default view controller for UIMainStoryboardFile 'Main' - perhaps the designated entry point is not set

原因分析：在StoryBoard中没有一个view controller设置了Initial Scene。

解决方案：在Storyboard中，选择一个view conroller作为story board的第一启动界面（勾选is Initial View Controller选项）