更新列表中的一行 (SwiftUI)

Question

我是编程的早起者，所以我知道从专家的角度来看这个问题可能很荒谬，但我几天后就陷入了这种情况。 在使用另一个按钮使用 TextField 存储项目后，我想通过使用按钮“编辑”（铅笔）来更新一行。

代码如下：

class Food: Hashable, Codable, Equatable {

    var id : UUID = UUID()
    var name : String

    init(name: String) {
        self.name = name
    }

    static func == (lhs: Food, rhs: Food) -> Bool {
        return lhs.name == rhs.name
    }

    func hash(into hasher: inout Hasher) {
    hasher.combine(name)
    }
}

---

class Manager: ObservableObject {

    let objectWillChange = PassthroughSubject<Void, Never>()

    @Published var shoppingChart: [Food] = []

    init() {

            let milk = Food(name: "Milk")
            let coffee = Food(name: "Coffee")

            shoppingChart.append(milk)
            shoppingChart.append(coffee)        
    }

    func newFood(name: String) {
        let food = Food(name: name)
        shoppingChart.insert(food, at: 0)
    }
}

---

struct ContentView: View {

    @ObservedObject var dm : Manager
    @State var isAddFoodOpened = false

    var body: some View {
        VStack {
            List {
                ForEach(self.dm.shoppingChart, id:\.self) { food in
                    HStack {
                    Text(food.name)
                    Image(systemName: "pencil")
                }
            }

        }
            self.buttonAdd
    }
}

    var buttonAdd: some View {
        Button(action: {
            self.isAddFoodOpened.toggle()
        }) {
            Text("Add")
        }
        .sheet(isPresented: $isAddFoodOpened) {
            Add(dm: self.dm, fieldtext: "", isAddFoodOpened: self.$isAddFoodOpened)
        }
    }
}

---

struct Add: View {

    @ObservedObject var dm : Manager
    @State var fieldtext : String = ""
    @Binding var isAddFoodOpened : Bool

    var body: some View {
        VStack {
        TextField("Write a food", text: $fieldtext)
        buttonSave
    }
    }

    var buttonSave : some View {
        Button(action: {
            self.dm.newFood(name: self.fieldtext)
            self.isAddFoodOpened = false
        }) {
            Text("Save")
        }
    }
}

Answer 1

@ObservedObject var dm : Manager 对象永远不会被初始化。

尝试像这样在 ContentView 中初始化 dm：

@ObservedObject var dm = Manager()

Answer 2

好的，如果我理解正确，您想使用“编辑”按钮更新/编辑一行。 这样就可以了：

struct ContentView: View {

@ObservedObject var dm : Manager
@State var isAddFoodOpened = false
@State var isEditOpened = false
@State var fieldtext : String = ""

var body: some View {
    VStack {
        List {
            ForEach(0..<self.dm.shoppingChart.count, id:\.self) { i in
                HStack {
                    Text(self.dm.shoppingChart[i].name)
                    Button(action: { self.isEditOpened.toggle() }) {
                        Image(systemName: "pencil")
                    }.sheet(isPresented: self.$isEditOpened) {
                        TextField(self.dm.shoppingChart[i].name, text: self.$fieldtext, onEditingChanged: { _ in
                            self.dm.shoppingChart[i].name = self.fieldtext
                        })
                    }
                }
            }
        }
        self.buttonAdd
    }
}

var buttonAdd: some View {
    Button(action: {
        self.isAddFoodOpened.toggle()
    }) {
        Text("Add")
    }
    .sheet(isPresented: $isAddFoodOpened) {
        Add(dm: self.dm, fieldtext: "", isAddFoodOpened: self.$isAddFoodOpened)
    }
}
}