onAppear 不允许 saving/updating 更改选择器值？

Question

我正在构建一个编辑视图，它允许用户更新列表项并将其保存回核心数据和列表。为此，我使用 .onAppear 操作将列表中的值传递到适当的字段中。

所有数据都被适当地传入，切换和文本字段让我可以轻松地进行更改并将它们保存回核心数据并更新列表项。但是，如果我尝试更改选择器值 (emojiChoice) 和 select 一个新值，选择器值不会更改或保存回 Core Data。

当我注释掉选择器变量 (emojiChoice) 的 onAppear 操作时，选择器现在允许我选择我想要的值并将其保存回 Core Data。我还有另一个视图，允许用户创建与此编辑视图几乎相同的项目，减去 onAppear 操作，效果也很好。选择器允许用户选择和表情符号。因为有很多表情符号，所以我创建了一个数组，而只是将 selected 表情符号的数组索引作为 Int 传递。

我该如何解决这个问题，让选择器显示要编辑的值并允许更改它？

这是编辑视图的代码：

struct editRemindr: View {
@Environment(\.managedObjectContext) var moc
@Environment(\.presentationMode) var presentationMode

let emojiList = EmojiList()
@ObservedObject var reminder: ReminderEntity
@State private var showingDeleteAlert = false

// Form Variables
@State var notifyOn = true
@State var emojiChoice = 0
@State var notification: String
@State var notes: String

// Delete Reminder Function
func deleteAction() {
    moc.delete(reminder)
    // try? self.moc.save()
    presentationMode.wrappedValue.dismiss()
}

// View Controller
var body: some View {
    Form {

        // On/Off Toggle
        Toggle(isOn: $notifyOn) {
            Text("On/Off")
        }

        // Emoji Picker
        Picker(selection: $emojiChoice, label: Text("Emoji")) {
            ForEach(0 ..< emojiList.emojis.count) {
                Text(self.emojiList.emojis[[=11=]])
            }
        }

        // Notification Text
        Section(header: Text("NOTIFICATION")) {
            HStack {
                TextField("Write your notification...", text: $notification)
                    .onReceive(notification.publisher.collect()) {
                        self.notification = String([=11=].prefix(60)) // <---- SET CHARACTER LIMIT
                }
                Text("\(notification.count) / 60")
                    .font(.caption)
                    .foregroundColor(.gray)
            }
        }

        // Notes Text
        Section(header: Text("NOTES")) {
            VStack {
                MultiLineTextField(text: $notes).frame(numLines: 6)
                    .padding(.top, 5)
                    .onReceive(notes.publisher.collect()) {
                        self.notes = String([=11=].prefix(240)) // <---- SET CHARACTER LIMIT
                }
                Text("\(notes.count) / 240")
                    .font(.caption)
                    .foregroundColor(.gray)
                    .frame(maxWidth: .infinity, alignment: .trailing)
            }
        }

        // Save Changes Button
        Section() {
            Button (action: {
                self.reminder.dateCreated = Date()
                self.reminder.notifyOn = self.notifyOn
                self.reminder.emojiChoice = Int64(self.emojiChoice)
                self.reminder.notification = self.notification
                self.reminder.notes = self.notes

                try? self.moc.save()

                self.presentationMode.wrappedValue.dismiss()
            }) {
                Text("SAVE CHANGES")
                    .fontWeight(.bold)
                    .foregroundColor(.white)
                    .font(.body)
            }        .padding()
                .frame(maxWidth: .infinity)
                .background(Color.green)
                .padding(.vertical, -6)
                .padding(.horizontal, -15)

            // Cancel Button
            Button(action: {
                self.presentationMode.wrappedValue.dismiss()
            }) {
                Text("Cancel")
                    .frame(maxWidth: .infinity)
            }
        }
    }

    // Make List Items Appear in Fields
    .onAppear(perform: {
        self.notifyOn = self.reminder.notifyOn
        self.emojiChoice = Int(self.reminder.emojiChoice)
        self.notification = self.reminder.notification ?? "unknown"
        self.notes = self.reminder.notes ?? "unknown"
    }) 
        .alert(isPresented: $showingDeleteAlert) {
            Alert(title: Text("Delete Reminder"), message: Text("Are you sure you want to delete this Reminder?"), primaryButton: .destructive(Text("Delete")) {
                self.deleteAction()
                }, secondaryButton: .cancel()
            )
    }
    .navigationBarTitle("Edit Reminder")
    .navigationBarItems(trailing: Button(action: {self.showingDeleteAlert = true
    }) {
        Image(systemName: "trash")

    })
} 

// Creates Text Limits
class TextLimit: ObservableObject {
    @Published var text = "" {
        didSet {
            if text.count > characterLimit && oldValue.count <= characterLimit {
                text = oldValue
            }
        }
    }
    let characterLimit: Int

    init(limit: Int = 5){
        characterLimit = limit
    }

}

如果它也有帮助的话，下面是带有列表的内容视图的代码。

struct ContentView: View {

@Environment(\.managedObjectContext) var moc
@FetchRequest(entity: ReminderEntity.entity(), sortDescriptors: [NSSortDescriptor(keyPath: \ReminderEntity.dateCreated, ascending: false)])
var reminder: FetchedResults<ReminderEntity>

@State private var showingAddScreen = false
@State var showWelcomeScreen = false

let emojiList = EmojiList()

//Toggle Control
@State var notifyOn = true

// Save Items Function
func saveItems() {
    do {
        try moc.save()
    } catch {
        print(error)
    }
}

// Delete Item Function
func deleteItem(indexSet: IndexSet) {
    let source = indexSet.first!
    let listItem = reminder[source]
    moc.delete(listItem)
}

// View Controller
var body: some View {
    VStack {
        NavigationView {
            ZStack (alignment: .top) {

                // List View
                List {
                    ForEach(reminder, id: \.self) { notification in
                        NavigationLink(destination: editRemindr(reminder: notification, notification: notification.notification ?? "unknown", notes: notification.notes ?? "unknown")) {
                            // Text within List View
                            HStack {
                                // MARK: TODO
                                // Toggle("NotifyOn", isOn: true)
                                // .labelsHidden() // Hides the label/title
                                Text("\(self.emojiList.emojis[Int(notification.emojiChoice)]) \(notification.notification!)")
                            } 
                        }
                    } 
                    .onDelete(perform: deleteItem)
                }

                    // Navigation Items
                    .navigationBarTitle("", displayMode: .inline)
                    .navigationBarItems(
                        leading:
                        HStack {

                            Button(action: {
                                self.showWelcomeScreen.toggle()
                            }) {
                                Image(systemName: "info.circle.fill")
                                    .font(.system(size: 24, weight: .regular))
                            }.foregroundColor(.gray)

                            // Positioning Remindr Logo on Navigation
                            Image("remindrLogoSmall")
                                .resizable()
                                .aspectRatio(contentMode: .fit)
                                //.frame(width: 60, height: 60, alignment: .center)
                                .padding(.leading, 83)
                                .padding(.top, -10)
                        },

                        // Global Settings Navigation Item
                        trailing: NavigationLink(destination: globalSettings()){
                            Image("settings")
                                .font(Font.title.weight(.ultraLight))
                        }.foregroundColor(.gray)
                )

                // Add New Reminder Button
                VStack {
                    Spacer()
                    Button(action: { self.showingAddScreen.toggle()
                    }) {
                        Image("addButton")
                            .renderingMode(.original)
                    }
                    .sheet(isPresented: $showingAddScreen) {

                        newRemindr().environment(\.managedObjectContext, self.moc)

                    } 
                }
            }
        }  .sheet(isPresented: $showWelcomeScreen) {
            welcomeScreen()
        }
    }
}

Answer 1

尝试以下方法

    // Emoji Picker
    Picker(selection: $emojiChoice, label: Text("Emoji")) {
        ForEach(0 ..< emojiList.emojis.count, id: \.self) { // << added id !!
            Text(self.emojiList.emojis[[=10=]])
        }
    }

Answer 2

我为选择器值创建了一个自定义绑定，它似乎可以解决问题。感谢 Reddit user End3r117 为我指明了正确的方向！

// View Controller
var body: some View {
    
    let reminderChoice = Binding(
        get: { Int(self.reminder.emojiChoice) },
        set: { self.reminder.emojiChoice = Int64([=10=]) }
    )
    return
        Form {
            
            // On/Off Toggle
            Toggle(isOn: $notifyOn) {
                Text("On/Off")
            }

            // Emoji Picker
            Picker(selection: reminderChoice, label: Text("Emoji")) {
                ForEach(0 ..< self.emojiList.emojis.count, id: \.self) {
                    Text(self.emojiList.emojis[[=10=]])
                }
            }

onAppear 不允许 saving/updating 更改选择器值？

onAppear not allowing saving/updating change from picker value?

xcode

picker

ios

swift

swiftui