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

Solution 1:

Make sure you have the following property declaration in your AppDelegate class:

var window: UIWindow?

Solution 2:

If you run your project on earlier than iOS 13.0, in that case you will face the problem. Because of iOS 13 and later, app launch differently than earlier versions.

• In iOS 13 and later, use UISceneDelegate objects to respond to life-cycle events in a scene-based app

• In iOS 12 and earlier, use the UIApplicationDelegate object to respond to life-cycle events.

When you launch the app in iOS 12 and earlier then UIApplicationMain class expect a window property in your AppDelegate class as like SceneDelegate has. So your problem will be solved if you add the following line in your AppDelegate class.

var window: UIWindow?

For Objective-C

@property (strong, nonatomic) UIWindow *window;

You can find more here App's Life Cycle.