SwiftUI發布的變數不更新視圖

背景關系：我正在嘗試使用 firebase 身份驗證和 firestore 來獲取用戶的資料。我遇到的問題是在完全獲取資料之前顯示視圖，這顯然會導致應用程式崩潰。話雖如此，我在我的應用程式委托中使用 firebase 身份驗證偵聽器來確保用戶在獲取用戶資料之前已通過身份驗證（這也在應用程式委托中完成，如下所示）

應用程式委托片段

class AppDelegate: NSObject, UIApplicationDelegate {
    var handle: AuthStateDidChangeListenerHandle?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
        FirebaseApp.configure()

        self.handle = Auth.auth().addStateDidChangeListener { (auth, user) in
            if (user != nil){
                print("UserAuthentication User authenticated in delegate")
                
                DatabaseDelegate().getUserInfo(UID: user!.uid, withCompletionHandler: {
                    print("got user data")
                })
                
            } else {
                print(" UserAuthentication User not authenticated in delegate")
                try! Auth.auth().signOut()
            }
        }
        return true
    }

這是我正在查詢并希望在資料加載完成時監聽的資料庫代碼：

class DatabaseDelegate: ObservableObject {
    @Published var userDataLoaded = Bool()

    func getUserInfo(UID: String, withCompletionHandler completionHandler: @escaping () -> Void) {
        database.collection("Users").document(UID).getDocument { (document, error) in
            if let document = document, document.exists {
                let data = document.data()!
                guard let UID = data["UUID"] as? String else { return }
                guard let Name = data["Name"] as? String else { return }
                guard let PhoneNumber = data["PhoneNumber"] as? String else { return }
                guard let StripeID = data["StripeID"] as? String else { return }
                
                self.userDataLoaded = true
                
                UserData.append(User(UID: UID, Name: Name, PhoneNumber: PhoneNumber, StripeID: StripeID, PurchasedContent: ["TEMP": true]))
                
                completionHandler()
            }
        }
    }
}

這是我想根據上面的 userDataLoaded 更新的 SwiftUI 視圖：

struct MainViewDelegate: View {
    //MARK: VARIABLES
    @State var showAnimation = true
    @State var locationHandler = LocationHandler()
    @ObservedObject var databaseDelegate = DatabaseDelegate()
    
    init(){
        //Check and enable user location
        locationHandler.requestAuthorisation()
    }

    var body: some View {
        VStack {
            //Check if data has finished loading, if not, show loading. Listen for changes when the data is finished loading and then present the tab view when it is.
            switch databaseDelegate.userDataLoaded {
                case true:
                    TabView {
                        HomeView()
                            .tabItem {
                                Label("Home", systemImage: "house")
                            }
                        CheckoutView()
                            .tabItem {
                                Label("Services", systemImage: "bag")
                            }
                        SettingsView()
                            .tabItem {
                                Label("Settings", systemImage: "gearshape")
                            }
                    }
                case false:
                    Text("Loading data")
            }
        }
    }
}

先謝謝了。我是 swiftui 的新手（從 uikit 過渡），我花了太多時間試圖解決這個愚蠢的問題

uj5u.com熱心網友回復：

1. 您正在使用 的兩個不同實體DatabaseDelegate，一個在 AppDelegate 中，一個在 MainViewDelegate 中。布林值僅在應用程式委托的實體中更新。

將您的身份驗證偵聽器移動到您的 DatabaseDelegate 中。

class AppDelegate: NSObject, UIApplicationDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
        FirebaseApp.configure()
        return true
    }
}

class DatabaseDelegate: ObservableObject {
    @Published var userDataLoaded = false

    private var handle: AuthStateDidChangeListenerHandle?
    
    init() {
        self.handle = Auth.auth().addStateDidChangeListener { (auth, user) in
           // .. etc
           self.getUserInfo(...)
        }
    }

    private func getUserInfo(UID: String, withCompletionHandler completionHandler: @escaping () -> Void) {
        database.collection("Users").document(UID).getDocument { (document, error) in
            // .. etc
            self.userDataLoaded = true
        }
    }
}

2. 您需要使用StateObject而不是ObservedObject因為您是在視圖內部初始化它，而不是從外部源注入它。

struct MainViewDelegate: View {
    @StateObject private var databaseDelegate = DatabaseDelegate()
}

如果你想使用 ObservedObject，你可以在外部創建它并注入到視圖中，如下所示：

var databaseDelegate = DatabaseDelegate()

MainViewDelegate(databaseDelegate: databaseDelegate)

struct MainViewDelegate: View {
    @ObservedObject var databaseDelegate: DatabaseDelegate
}

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