SwiftUI-删除列表时绑定数组中有趣的问题

Question

这与我以前遇到的问题非常相似（没有人可以回答）。我正在尝试创建一个可以在其中编辑元素的动态列表。据我所知，推荐的方法是拥有一个带有绑定的EditView，它由LIst中的NavigationLink激活。所以，我做到了。它似乎一开始就可以工作，直到我意识到每个NavigationLink只能工作一次（这是一个错误吗？）。我不认为我会做错什么导致这种情况。然后，我想也许可以通过将List中的EditView切换到就地编辑。我设计了一种理论方法来执行此操作，然后在我的代码中进行了尝试。起初，它看起来很棒。但是，如果启用“就地编辑”，则删除最后一个元素会导致“致命错误：索引超出范围”。我将整个代码捆绑到一个文件中，因此您只需复制并粘贴到Xcode中即可自己尝试。我开始认为也许XCode 11.3.1距完成文章还很远。

import SwiftUI

struct EditView: View {
    @Binding var person:Person
    var body: some View {
        HStack{
            Group{
                TextField("name1", text: $person.name1)
                TextField("name2", text: $person.name2)
            }.frame(width:200)
            .font(.headline)
                .padding(.all, 3)
                .overlay(RoundedRectangle(cornerRadius: 4).stroke(Color.blue, lineWidth: 1))
        }.navigationBarTitle("Edit entry")
    }
}
struct Person:Identifiable, Equatable{
    var id:UUID
    var name1:String
    var name2:String
    var isEditable:Bool
}
class PersonList: ObservableObject {
    @Published var individuals = [Person]()// Array of Person structs
}
struct ContentView: View {
    @ObservedObject var people = PersonList()// people.individuals = [Person] array
    @State private var edName1:String = "" //temporary storage for adding new member
    @State private var edName2:String = "" //temporary storage for adding new member
    @State private var allowEditing:Bool = false
    var elementCount:Int{
        let c = people.individuals.count
        return c
    }
    // arrays for testing - adds random names from these (if input field '1st name' is empty)...
    var firstNames = ["Nick","Hermes","John","Hattie","Nicola","Alan", "Dwight", "Richard","Turanga", "Don","Joey"]
    var surnames = ["Farnsworth","Fry","Wong","Zoidberg","Conrad","McDougal","Power","Clampazzo","Brannigan","Kroker","Leela"]
    var body: some View {
        NavigationView{
            VStack{
                HStack{
                    Text("Add person:")
                        .padding(.all, 5)
                        .frame(alignment: .leading)
                    TextField("1st name", text: $edName1)
                        .frame(width:150)
                        .padding(.all, 5)
                        .overlay(RoundedRectangle(cornerRadius: 8).stroke(Color.blue, lineWidth: 2))
                    TextField("2nd name", text: $edName2)
                        .frame(width:150)
                        .padding(.all, 5)
                        .overlay(RoundedRectangle(cornerRadius: 8)
                            .stroke(Color.blue, lineWidth: 2))
                    // 🆗 Button...
                    Image(systemName: "plus.circle")
                        .font(.largeTitle)
                        .foregroundColor(.orange)
                        .onTapGesture {
                            if self.edName1 == ""{
                                self.edName1 = self.firstNames.randomElement() ?? "⁉️"
                                self.edName2 = self.surnames.randomElement() ?? "⁉️"
                            }
                            self.people.individuals.append(Person(id: UUID(), name1: self.edName1, name2: self.edName2, isEditable: false))
                            self.edName1 = ""
                            self.edName2 = ""
                            print("Element count: \(self.elementCount)")
                    }
                    Toggle(isOn: $allowEditing){Text("edit in place")}.padding(.all,5).overlay(RoundedRectangle(cornerRadius: 8)
                        .stroke(Color.red, lineWidth: 2))
                    Spacer()
                    // 🆗 Button...sort
                    Image(systemName: "arrow.up.arrow.down.square")
                        .font(.title)
                        .padding(.all,4)
                        .foregroundColor(.blue)
                        .onTapGesture {
                            self.people.individuals.sort{ // sort list alphabetically by name2
                                $0.name2 < $1.name2
                            }
                    }
                    // 🆗 Button...reverse order
                    Image(systemName: "arrow.uturn.up.square")
                        .font(.title)
                        .padding(.all,8)
                        .foregroundColor(.blue)
                        .onTapGesture {
                            self.people.individuals.reverse()
                    }
                }.padding(.all,8)
                    .overlay(RoundedRectangle(cornerRadius: 12)
                        .stroke(Color.orange, lineWidth: 2))
                List{
                    ForEach(people.individuals){individual in
                        HStack{
                            if self.allowEditing{
                                //Toggle to edit in place
                                Toggle(isOn: self.$people.individuals[self.people.individuals.firstIndex(of:individual)!].isEditable){
                                    Text("edit").font(.headline).foregroundColor(.green).opacity(individual.isEditable ? 1.0 : 0.4)
                                }.frame(width:100)
                            }

                            if individual.isEditable{
                                EditView(person: self.$people.individuals[self.people.individuals.firstIndex(of:individual)!])
                            }
                            else{
                                NavigationLink(destination:EditView(person: self.$people.individuals[self.people.individuals.firstIndex(of:individual)!])){
                                    Text("\(individual.name1) \(individual.name2)")
                                        .frame(width: 200, alignment: .leading)
                                        .padding(.all, 3)
                                }// link
                            }
                        }
                    }.onDelete(perform: deleteRow)
                }
            }.navigationBarTitle("People List (\(elementCount))")
        }.navigationViewStyle(StackNavigationViewStyle())
    }
    func deleteRow(at offsets: IndexSet){
        self.people.individuals.remove(atOffsets: offsets)
    }
}


struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
            .environment(\.colorScheme, .dark)
    }
}

任何人都可以阐明这一点吗？我找不到任何可以帮助我的东西。更新：感谢'krjw'指出一次性使用NavLink问题在实际设备上不会发生。“最后一个元素删除”问题似乎与元素视图中存在活动绑定有关。

Answer 1

尽管有我的评论，但我还是试图找到一种解决方案，但我可能会找到一个可以接受的解决方案：

我不得不重塑Person ...当然，整个索引都是问题，但是我无法确切地知道何时发生。我什至尝试使用本地@State来更新视图，然后更新@ObservedObject ...]的数组

这里有一些链接可能有助于进一步调查...

Swift UI detail remove

How do I set the toggle state in a foreach loop in SwiftUI

struct EditView: View {
    @ObservedObject var person: Person
    var body: some View {
        HStack{
            Group{
                TextField("name1", text: $person.name1)
                TextField("name2", text: $person.name2)
            }//.frame(width:200)
            .font(.headline)
                .padding(.all, 3)
                .overlay(RoundedRectangle(cornerRadius: 4).stroke(Color.blue, lineWidth: 1))
        }.navigationBarTitle("Edit entry")
    }
}

struct RowView: View {
    @Binding var allowEditing: Bool
    @ObservedObject var individual: Person

    var body: some View {
        HStack {
            if self.allowEditing {
                //Toggle to edit in place
                Toggle(isOn: self.$individual.isEditable){
                    Text("edit").font(.headline).foregroundColor(.green).opacity(self.individual.isEditable ? 1.0 : 0.4)
                }//.frame(width:100)
            }

            if self.individual.isEditable{
                EditView(person: self.individual)
            }
            else{
                NavigationLink(destination:EditView(person: self.individual)){
                    Text("\(self.individual.name1) \(self.individual.name2)")
                        //.frame(width: 200, alignment: .leading)
                        .padding(.all, 3)
                }// link
            }
        }
    }
}


class Person: ObservableObject, Identifiable {
    @Published var id:UUID
    @Published var name1:String
    @Published var name2:String
    @Published var isEditable:Bool

    init(id: UUID, name1: String, name2: String, isEditable: Bool){
        self.id = id
        self.name1 = name1
        self.name2 = name2
        self.isEditable = isEditable
    }
}

struct ContentView: View {
    @State var people = [Person]()//try! ObservableArray<Person>(array: []).observeChildrenChanges(Person.self)// people.individuals = [Person] array

    @State private var edName1:String = "" //temporary storage for adding new member
    @State private var edName2:String = "" //temporary storage for adding new member
    @State private var allowEditing:Bool = false

    // arrays for testing - adds random names from these (if input field '1st name' is empty)...
    var firstNames = ["Nick","Hermes","John","Hattie","Nicola","Alan", "Dwight", "Richard","Turanga", "Don","Joey"]
    var surnames = ["Farnsworth","Fry","Wong","Zoidberg","Conrad","McDougal","Power","Clampazzo","Brannigan","Kroker","Leela"]

    var body: some View {
        NavigationView{
            VStack{
                HStack{
                    Text("Add person:")
                        .padding(.all, 5)
                        .frame(alignment: .leading)
                    TextField("1st name", text: $edName1)
                        //.frame(width:150)
                        .padding(.all, 5)
                        .overlay(RoundedRectangle(cornerRadius: 8).stroke(Color.blue, lineWidth: 2))
                    TextField("2nd name", text: $edName2)
                        //.frame(width:150)
                        .padding(.all, 5)
                        .overlay(RoundedRectangle(cornerRadius: 8)
                            .stroke(Color.blue, lineWidth: 2))
                    // 🆗 Button...
                    Image(systemName: "plus.circle")
                        .font(.largeTitle)
                        .foregroundColor(.orange)
                        .onTapGesture {
                            if self.edName1 == ""{
                                self.edName1 = self.firstNames.randomElement() ?? "⁉️"
                                self.edName2 = self.surnames.randomElement() ?? "⁉️"
                            }
                            self.people.append(Person(id: UUID(), name1: self.edName1, name2: self.edName2, isEditable: false))
                            self.edName1 = ""
                            self.edName2 = ""
                            print("Element count: \(self.people.count)")
                    }
                    Toggle(isOn: $allowEditing){Text("edit in place")}.padding(.all,5).overlay(RoundedRectangle(cornerRadius: 8)
                        .stroke(Color.red, lineWidth: 2))
                    Spacer()
                    // 🆗 Button...sort
                    Image(systemName: "arrow.up.arrow.down.square")
                        .font(.title)
                        .padding(.all,4)
                        .foregroundColor(.blue)
                        .onTapGesture {
                            self.people.sort{ // sort list alphabetically by name2
                                $0.name2 < $1.name2
                            }
                    }
                    // 🆗 Button...reverse order
                    Image(systemName: "arrow.uturn.up.square")
                        .font(.title)
                        .padding(.all,8)
                        .foregroundColor(.blue)
                        .onTapGesture {
                            self.people.reverse()
                    }
                }.padding(.all,8)
                    .overlay(RoundedRectangle(cornerRadius: 12)
                        .stroke(Color.orange, lineWidth: 2))
                List {
                    ForEach(self.people) { person in
                        RowView(allowEditing: self.$allowEditing, individual: person)
                    }.onDelete(perform: deleteRow)
                }
            }.navigationBarTitle("People List (\(self.people.count))")
        }.navigationViewStyle(StackNavigationViewStyle())
    }

    func deleteRow(at offsets: IndexSet){
        self.people.remove(atOffsets: offsets)
        print(self.people.count)
    }
}
我希望这会有所帮助！