如何解决核心数据，更新问题改为复制
我是 Swift UI 的新手。你能帮我更新核心数据吗？ 这是问题的关键：
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 - 按添加新目标后出现。
- RingView - 带有目标环（类似于活动环机制）和所有数据的视图。
问题的关键在于：
- 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 传递出 2 个项目（一个字符串和一个双精度）。
- 然后，在按下最近创建的目标后，我出现在环视图中。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 项（双项）并将其发回。所以它可以在 FirstView 上更新。
结果： 而不是更新这个 3-d 项目，它似乎只是在前一个目标下方的第一个视图上创建一个全新的目标。 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(
$neededSum,from: 0,through: 100000,by: 25,sensitivity: .high)
}
Button(action: addGoal) {
Text("Add Goal")
}
.disabled(neededSum == 0.0)
.disabled(goalTitle == "")
.navigationTitle("Edit")
}
}
}
private func addGoal(){
let goal = NewGoal(context: context)
goal.goalTitle = goalTitle
goal.dateAdded = Date()
goal.neededSum = neededSum
do{
try context.save()
presentationMode.wrappedValue.dismiss()
}catch let err{
print(err.localizedDescription)
}
}
我的代码（RingView 代码）：
struct RingView: View {
@State private var isFocusedSum = false
@State private var yournewSum:Double = 0.0
var goalItem: NewGoal?
var Sum:Double
var GTitle:String
@Environment(\.managedObjectContext) var context
@Environment(\.presentationMode) var presentationMode
@FetchRequest var results: FetchedResults<NewGoal>
init(GTitle: String,Sum: Double){
self.GTitle = GTitle
self.Sum = Sum
let predicate = NSPredicate(format:"goalTitle == %@",GTitle)
self._results=FetchRequest(
entity: NewGoal.entity(),sortDescriptors: [NSSortDescriptor(keyPath: \NewGoal.dateAdded,predicate: predicate,animation: .easeInOut
)
}
var body: some View {
ZStack{
ForEach(results) { item in
RingShape(percent:(yournewSum/item.neededSum*100),startAngle: -90,drawnClockwise: false) /// Ring
.stroke(style: StrokeStyle(lineWidth: 10,lineCap: .round))
.fill(AngularGradient(gradient: Gradient(colors: [.red,.pink,.red]),center: .center))
.frame(width: 155,height: 155)
HStack(alignment: .top){
Spacer()
Button(action: addSum) { ///BUTTON TO Update
Image(systemName: "gear")
}
.clipShape(Circle())
}
VStack(alignment: .trailing,spacing: 0.0){
Spacer()
Text("$\(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,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)
}
}
解决方法
您永远不会给 var goalItem: NewGoal? 要更新的项目的初始值。
尝试更换这个
RingView(GTitle: item.goalTitle ?? "",Sum: item.neededSum)
与
RingView(goalItem: item,GTitle: item.goalTitle ?? "",Sum: item.neededSum)
当然，您必须将 RingView 的初始化程序更改为
init(goalItem: NewGoal? = nil,GTitle: String,Sum: Double){
并将这一行添加到初始值设定项
self.goalItem = goalItem
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