The app delegate must implement the window property if it wants to use a main storyboard file.

前言

iOS 小白，纯属记录，方便自己查找，大牛勿喷

The app delegate must implement the window property if it wants to use a main storyboard file.

xcode 11中AppDelegate中未声明"@property (strong, nonatomic) UIWindow * window;而是在SceneDelegate进行UIwindow的声明。

在声明"@property (strong, nonatomic) UIWindow * window即可解决。