限制列表的对象数量 - SwiftUi

Posted 2023-02-24

【中文标题】限制列表的对象数量 - SwiftUi

【英文标题】：Limit List's objects amount - SwiftUi

【发布时间】：2021-07-21 09:20:01

【问题描述】：

我的 WatchOS 应用在 Core Data 上运行。那里有 2 个视图：

FirstView - 带有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。

我还添加了List，因为我想在我的应用程序中使用.onDelete。

我试图限制用户创建无限数量的目标。我想给一个添加最多 10 个目标的机会，然后 AddGoal 按钮变为禁用。你有什么建议吗？

第一次查看代码：

struct FirstView: View 
@Environment(\.managedObjectContext) var context
    @FetchRequest (
    entity:NewGoal.entity(),
       sortDescriptors:[NSSortDescriptor(keyPath: \NewGoal.dateAdded, ascending: false)],
        animation: .easeInOut )

var results:FetchedResults<NewGoal>
var body: some View 
        VStack
        VStack(alignment: .leading)
            NavigationLink(
                    destination: AddGoalView(),
                    label: 
                        Text("Set Money Goal"))
                        Text("10/10")

             VStack(alignment: .leading)
                List
                ForEach(results) item in
                    NavigationLink(
                        destination: TABmodule(goalItem: item, GTitle: item.goalTitle ?? "", Sum: item.neededSum, summarize: item.yourSum),
                            label: 
                                HStack
                                        HStack(alignment: .center, spacing:0)
                                            Text(String(item.indDatenum))
                                            Text(item.pickedValueDateS ?? "")
                                        

                                VStack(alignment: .leading)
                                    Text(item.goalTitle ?? "")
          
                                    HStack(spacing: 0)
                                        Text("$\(item.yourSum, specifier: "%.f")")
                                        Text("/ $\(item.neededSum, specifier: "%.f")")
                                    
                                
                                
                    ).clipShape(RoundedRectangle(cornerRadius: 9))
                    
                 .onDelete(perform: deleteGoal2)
                .listStyle(PlainListStyle())

                
            
        
    
func deleteGoal2(at offsets: IndexSet) 
    for index in offsets 
        let item = results[index]
        context.delete(item)
    
    do
        try context.save()
    catch let err
            print(err.localizedDescription)
            

AddGoalView 上的 AddGoal 函数：

    private func addGoal()
    
    if index == 0 
        pickedValueDateS = "W"
        pickedValueDateN = 7 * indexnum
        pickedValueDateN1 = 7 * indexnum
         else if index == 1
            pickedValueDateS = "M"
            pickedValueDateN = 30 * indexnum
            pickedValueDateN1 = 30 * indexnum
         else if index == 2
            pickedValueDateS = "Y"
            pickedValueDateN = 365 * indexnum
            pickedValueDateN1 = 365 * indexnum
     else 
        pickedValueDateS = "N/A"
        pickedValueDateN = 1
    
    let goal = NewGoal(context: context)
    goal.goalTitle = goalTitle
    goal.dateAdded = Date()
    goal.neededSum = neededSum
    goal.pickedValueDateS = pickedValueDateS
    goal.allNewSum = allNewSum
    goal.pickedValueDateN = Int64(pickedValueDateN)////ALL DAYS
    goal.pickedValueDateN1 = Int64(pickedValueDateN1)////MINUS DAYS
    goal.dayChange = Int64(daychange)
    goal.indDate = Int64(index)
    goal.indDatenum = Int64(indexnum)
    
    
    do
        try context.save()
        presentationMode.wrappedValue.dismiss()
    catch let err
        print(err.localizedDescription)
        
    

【参考方案1】：

将此添加到您想要禁用的任何View，例如NavigationLink，这样用户就无法访问View

.disabled(results.count >= 10)