如何将展开和折叠列表行与 Core Data 元素一起使用？答案

【问题标题】：How can I use Expand and Collapse List Rows with Core Data elements?如何将展开和折叠列表行与 Core Data 元素一起使用？
【发布时间】：2020-07-06 16:45:32
【问题描述】：

struct AppointmentView: View
{
    @Environment(\.managedObjectContext) var managedObjectContext
    @FetchRequest(entity: Appoint.entity(), sortDescriptors: [NSSortDescriptor(keyPath: \Appoint.title , ascending: true)])
    var appointments_title: FetchedResults<Appoint>
    @State var showAddDate = false
    @State var sectionState: [Int: Bool] = [:]
    
    var body: some View
    {
        NavigationView
        {
            List
            {
                    ForEach(appointments_title)
                    {
                        order in
                        HStack
                        {
                            Text("\(order.title)").font(.headline)
                            Spacer()
                            Text("\(order.date, formatter: ContentView.self.taskDateFormat)").font(.headline)
                        }.contentShape(Rectangle())
                            .onTapGesture
                            {
                                self.sectionState[order] = !self.isExpanded(order)
                            }
                        if self.isExpanded(order)
                        {
                            Text("\(order.description)”)
                        }
                    }
             }
         
            .navigationBarTitle("My Appointment")
            .navigationBarItems(trailing: Button(action: {self.showAddDate = true}, label: {Image(systemName: "plus.circle").resizable().frame(width: 32, height: 32, alignment: .center)}))
            .sheet(isPresented: $showAddDate) {AddDate().environment(\.managedObjectContext, self.managedObjectContext)}
        }
    }
    func isExpanded(_ order:Int) -> Bool
    {
        sectionState[order] ?? false
    }
}

当我尝试运行此代码时，我会收到此错误消息；
无法将“FetchedResults ”类型的值转换为预期
参数类型'Range '

有没有办法将 'FetchedResults ' 转换为 'Range ' ？

【问题讨论】：

标签： swift core-data swiftui

【解决方案1】：

我想出了一些东西，它起作用了。基本上，我只是在我的 .xcdatamodeld 文件中添加另一个布尔类型的属性并将其称为“isExpanded”。每次添加新条目时，我都会将其布尔属性设置为 false。

struct AppointmentView: View
{
    @Environment(\.managedObjectContext) var managedObjectContext
    @FetchRequest(entity: Appoint.entity(), sortDescriptors: [NSSortDescriptor(keyPath: \Appoint.title , ascending: true)])
    var appointments_title: FetchedResults<Appoint>
    @State var showAddDate = false
    //@State var sectionState: [Int: Bool] = [:]
    
    var body: some View
    {
        NavigationView
        {
            List
            {
                    ForEach(appointments_title)
                    {
                        order in
                        HStack
                        {
                            Text("\(order.title)").font(.headline)
                            Spacer()
                            Text("\(order.date, formatter: ContentView.self.taskDateFormat)").font(.headline)
                        }.contentShape(Rectangle())
                            .onTapGesture
                            {
                                order.isExpanded.toggle()
                            }
                        if order.isExpanded
                            {
                                Text("\(order.description)”)
                            }
                            else
                            {
                                EmptyView()
                            }
                    }
             }
         
            .navigationBarTitle("My Appointment")
            .navigationBarItems(trailing: Button(action: {self.showAddDate = true}, label: {Image(systemName: "plus.circle").resizable().frame(width: 32, height: 32, alignment: .center)}))
            .sheet(isPresented: $showAddDate) {AddDate().environment(\.managedObjectContext, self.managedObjectContext)}
        }
    }
    /*func isExpanded(_ order:Int) -> Bool
    {
        sectionState[order] ?? false
    }*/
}

【讨论】：