核心数据，更新问题（改为复制）

Question

我是 Swift UI 的新手。你能帮我更新核心数据吗？下面是一个问题的重点：

我正在构建一个 WatchOS 应用程序。那里有 3 个视图：

FirstView - 带有用于添加新目标和已添加目标列表的按钮的视图。
AddGoalView - 在按下添加新目标后出现。
RingView - 带有目标环的视图（类似于 activity 环机制）和所有显示的数据。

问题的重点是下一个：

添加新目标后一切正常。数据从 AddGoalView 正确传递到 FirstView。我只需要从 AddGoalView 传递 2 个项目（一个 String 和一个 Double）。
然后，在按下最近创建的目标后，我出现在环形视图中。我成功地传递了 2 个项目（我提到的 String 和 Double）。
在 RingView 上，我想更新第 3 个项目（双）并将其发回。所以它可以在 FirstView 上更新。

结果：它似乎没有更新这个 3-d 项目，而是在先前目标下方的第一个视图上创建了一个全新的目标。 Photo

我的代码（FirstView）：

struct FirstView: View {
    @FetchRequest (
        entity:NewGoal.entity(),
        sortDescriptors:[NSSortDescriptor(keyPath: \NewGoal.dateAdded, ascending: false)],
        animation: .easeInOut )
    
    var results:FetchedResults<NewGoal>
    @State var showMe = false
    
    var body: some View {
        ScrollView{
            VStack{
                VStack(alignment: .leading){
                    Text("My Goals:")
                    NavigationLink(
                        destination: AddGoalView(),
                        isActive: $showMe,
                        label: {
                            Image(systemName: "plus")
                            Text("Set Money Goal")
                        })
                    
                    Text("Recents:")
                    ForEach(results){ item in
                        VStack(alignment: .leading){
                            NavigationLink(
                                destination: RingView(GTitle: item.goalTitle ?? "", Sum: item.neededSum),
                                label: {
                                    HStack{
                                        Image(systemName: "gear")
                                        VStack(alignment: .leading){
                                            Text(item.goalTitle ?? "")
                                            HStack{
                                                Text("$\(item.yourSum, specifier: "%.f")") ///This item doesn't update
                                                Text("/ $\(item.neededSum, specifier: "%.f")")
                                            }
                                        }
                                    }
                                })
                        }
                    }
                }
            }
        }
    }
}

我的代码（AddGoalView）：

struct AddGoalView: View {
    @State private var goalTitle = ""
    @State private var showMe:Bool = true
    @State private var neededSum:Double = 0.0
    @State private var isFocusedNum = false
    @Environment(\.managedObjectContext) var context
    @Environment(\.presentationMode) var presentationMode
    var body: some View {
        ScrollView{
            VStack (alignment: .leading, spacing: 6){
                TextField("Goal Name...", text: $goalTitle)
                HStack{
                    Text("$\(neededSum, specifier: "%.f")")
                        .overlay(
                            RoundedRectangle(cornerRadius: 9)
                                .stroke(isFocusedNum ? Color.red : Color.white, lineWidth: 1)
                                .opacity(1.0))
                        .focusable(true) { newState in isFocusedNum = newState}
                        .animation(.easeInOut(duration: 0.1), value: isFocusedNum)
                        .digitalCrownRotation(
                            $neededSum,
                            from: 0,
                            through: 100000,
                            by: 25,
                            sensitivity: .high)
                }
                Button(action: addGoal) {
                    Text("Add Goal")
                }
                .disabled(neededSum == 0.0)
                .disabled(goalTitle == "")
                .navigationTitle("Edit")
            }
        }
    }
    private func addGoal(){
        let goal = NewGoal(context: context)
        goal.goalTitle = goalTitle
        goal.dateAdded = Date()
        goal.neededSum = neededSum
        do{
            try context.save()
            presentationMode.wrappedValue.dismiss()
        }catch let err{
            print(err.localizedDescription)
        }
    }

我的代码（RingView 代码）：

struct RingView: View {
    @State private var isFocusedSum = false
    @State private var yournewSum:Double = 0.0
    var goalItem: NewGoal?
    var Sum:Double
    var GTitle:String
    @Environment(\.managedObjectContext) var context
    @Environment(\.presentationMode) var presentationMode
    @FetchRequest var results: FetchedResults<NewGoal>
    init(GTitle: String, Sum: Double){
        self.GTitle = GTitle
        self.Sum = Sum
        let predicate = NSPredicate(format:"goalTitle == %@", GTitle)
        self._results=FetchRequest(
            entity: NewGoal.entity(),
            sortDescriptors: [NSSortDescriptor(keyPath: \NewGoal.dateAdded, ascending: false)],
            predicate: predicate,
            animation: .easeInOut
        )
    }
    
    var body: some View {
        ZStack{
            ForEach(results) { item in
                RingShape(percent:(yournewSum/item.neededSum*100), startAngle: -90, drawnClockwise: false) /// Ring
                    .stroke(style: StrokeStyle(lineWidth: 10, lineCap: .round))
                    .fill(AngularGradient(gradient: Gradient(colors: [.red, .pink, .red]), center: .center))
                    .frame(width: 155, height: 155)
                HStack(alignment: .top){
                    Spacer()
                    Button(action: addSum) { ///BUTTON TO Update
                        Image(systemName: "gear")
                    }
                    .clipShape(Circle())
                }
                VStack(alignment: .trailing, spacing: 0.0){
                    Spacer()
                    Text("$\(yournewSum, specifier: "%.f")")     /// Here is the data I want to change via Digital Crown and update
                        .font(.title3)
                        .overlay(
                            RoundedRectangle(cornerRadius: 7)
                                .stroke(Color.white, lineWidth: 2)
                                .opacity(isFocusedSum ? 1.0:0.0)
                        )
                        .focusable(true) { newState in isFocusedSum = newState}
                        .animation(.easeInOut(duration: 0.3), value: isFocusedSum)
                        .digitalCrownRotation(
                            $yournewSum,
                            from: 0,
                            through: Double((item.neededSum)),
                            by: 10,
                            sensitivity: .high)
                    Text("/ $\(item.neededSum, specifier: "%.f")") ///Here is the Double data I entered in AddGoalView
                        .font(.caption)
                }
                .frame(width: 200, height: 230)
                .padding(.top, 7)
                VStack(alignment: .center, spacing: 1.0){
                    Text(item.goalTitle ?? "Your Goal Name") ///Here is the String data I entered in AddGoalView
                        .foregroundColor(.gray)
                }
                .padding(.top, 200.0)
            }
        }
        .padding([.top, .leading, .trailing], 5.0)
        
    }
    private func addSum(){
        let goal = goalItem == nil ? NewGoal(context: context): goalItem
        goal?.yourSum = yournewSum //// I am trying to update the Data here, but after running the func it creates a duplicate.
        do{
            try context.save()
            presentationMode.wrappedValue.dismiss()
        } catch let err{
            print(err.localizedDescription)
        }
    }

Answer 1

您从未给 var goalItem: NewGoal? 要更新的项目的初始值。

尝试替换这个

RingView(GTitle: item.goalTitle ?? "", Sum: item.neededSum)

和

RingView(goalItem: item, GTitle: item.goalTitle ?? "", Sum: item.neededSum)

当然，您必须将 RingView 的初始值设定项更改为

init(goalItem: NewGoal? = nil, GTitle: String, Sum: Double){

并将这一行添加到初始化程序

self.goalItem = goalItem

核心数据，更新问题（改为复制）

Core Data, Problem with updating (duplicating instead)

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swiftui