AppDelegate:

import UIKit
import CoreData//包含App的部分生命周期函数(钩子函数),也有其余函数(如推送)
@main
class AppDelegate: UIResponder, UIApplicationDelegate {func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {// Override point for customization after application launch.print("App启动")return true}// MARK: UISceneSession Lifecycle//iOS的App只有一个场景(只有一个窗口)func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {// Called when a new scene session is being created.// Use this method to select a configuration to create the new scene with.print("即将创建一个窗口时.在此可配置一个可视窗口")return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)}func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {// Called when the user discards a scene session.// If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.// Use this method to release any resources that were specific to the discarded scenes, as they will not return.print("用户关闭了某个窗口")}// MARK: - Core Data stacklazy var persistentContainer: NSPersistentContainer = {/*The persistent container for the application. This implementationcreates and returns a container, having loaded the store for theapplication to it. This property is optional since there are legitimateerror conditions that could cause the creation of the store to fail.*/let container = NSPersistentContainer(name: "Todos")container.loadPersistentStores(completionHandler: { (storeDescription, error) inif let error = error as NSError? {// Replace this implementation with code to handle the error appropriately.// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development./*Typical reasons for an error here include:* The parent directory does not exist, cannot be created, or disallows writing.* The persistent store is not accessible, due to permissions or data protection when the device is locked.* The device is out of space.* The store could not be migrated to the current model version.Check the error message to determine what the actual problem was.*/fatalError("Unresolved error \(error), \(error.userInfo)")}})return container}()// MARK: - Core Data Saving supportfunc saveContext () {let context = persistentContainer.viewContextif context.hasChanges {do {try context.save()} catch {// Replace this implementation with code to handle the error appropriately.// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.let nserror = error as NSErrorfatalError("Unresolved error \(nserror), \(nserror.userInfo)")}}}}

SceneDelegate:

import UIKit//包含App的UI方面的生命周期函数,也有其余函数(如从别的App跳转回来时)
class SceneDelegate: UIResponder, UIWindowSceneDelegate {var window: UIWindow?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).print("若使用IB,则自动创建可视窗口;若不使用IB,则可在此利用window属性(可视窗口),然后用代码设定App的首页vc")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 necessarily discarded (see `application:didDiscardSceneSessions` instead).print("窗口/App已经断开连接(1.关闭App时调用,2.退到后台后不久调用)")}//App主要有三种状态:被关闭,在前台,在后台//下面两个方法对应的范围更广,如App关闭时,用户点击推送横幅后打开App,也会调用sceneDidBecomeActive,此时可清楚右上角角标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.print("窗口/App从非活跃-->活跃(已经被激活)")}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).print("窗口/App从活跃-->非活跃(即将被挂起)")}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.print("窗口/App从后台-->前台(即将回到前台)")}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.print("窗口/App从前台-->后台(已经进入后台)")// Save changes in the application's managed object context when the application transitions to the background.(UIApplication.shared.delegate as? AppDelegate)?.saveContext()}}