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Chapter 17. Improved data model

Hello. In Xcode 11 I have to separate files AppDelegate.swift and SceneDelegate.swift. In which of them I should put the code explained in this chapter?

    var window: UIWindow?
  let dataModel = DataModel()

	func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    let navigationController = window!.rootViewController as! UINavigationController
    let controller = navigationController.viewControllers[0] as! AllListsViewController
    controller.dataModel = dataModel
    return true
	}

    saveData()
2 Likes

Hi @ucelme, welcome to the forum community! From what I can tell, it appears that the code you have there would be in the AppDelegate.swift file. Generally the AppDelegate file will have the didFinishLaunchingWithOptions instance method which “tells the delegate that the launch process is almost done and the app is almost ready to run.”

Best,
Gina

However, in iOS 13, window will be returned as nil, due to the UIScene additions. I had that problem with the Checklists app, and MyLocations app, and had to change my target to iOS 12, and remove the SceneDelegate.swift file, remove the UISceneSession code in AppDelegate.swift, and modify Info.plist to work.

2 Likes

You put the code in this section in the SceneDelegate method :

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
    // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
    // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
    let navigationController = window!.rootViewController as! UINavigationController
     let controller = navigationController.viewControllers[0] as! AllListViewController
     controller.dataModel = dataModel
    guard let _ = (scene as? UIWindowScene) else { return }
}
1 Like

I tried this code, but saving not works. All data dissapears when I reload the app. Also I tried to run original project from materials chapters, but also saving data not works.

import UIKit

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?
    let dataModel = DataModel()
    
    func saveData() {
    dataModel.saveChecklists()
    }

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
        let navigationController = window!.rootViewController as! UINavigationController
         let controller = navigationController.viewControllers[0] as! AllListsViewController
         controller.dataModel = dataModel
        guard let _ = (scene as? UIWindowScene) else { return }
    }

    func sceneDidDisconnect(_ scene: UIScene) {
        // Called as the scene is being released by the system.
        // This occurs shortly after the scene enters the background, or when its session is discarded.
        // Release any resources associated with this scene that can be re-created the next time the scene connects.
        // The scene may re-connect later, as its session was not neccessarily discarded (see `application:didDiscardSceneSessions` instead).
        saveData()
    }

    func sceneDidBecomeActive(_ scene: UIScene) {
        // Called when the scene has moved from an inactive state to an active state.
        // Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
    }

    func sceneWillResignActive(_ scene: UIScene) {
        // Called when the scene will move from an active state to an inactive state.
        // This may occur due to temporary interruptions (ex. an incoming phone call).
    }

    func sceneWillEnterForeground(_ scene: UIScene) {
        // Called as the scene transitions from the background to the foreground.
        // Use this method to undo the changes made on entering the background.
    }

    func sceneDidEnterBackground(_ scene: UIScene) {
        // Called as the scene transitions from the foreground to the background.
        // Use this method to save data, release shared resources, and store enough scene-specific state information
        // to restore the scene back to its current state.

        // Save changes in the application's managed object context when the application transitions to the background.
        saveData()
    }

}

I do have the same problem!

By a quick searching, I found that it’s something about UIWindow init() move to SceneDelegate.swift from AppDelegate.swift. Could anyone help us here?

@ucelme Does this work for you now?

@doraemonchi Do you still have issues with this?