SwiftUI：如何在另一个视图中更新传递的数组项

Question

我正在尝试将具有键入新值的数组项更新到Textfield中，但是List不会使用已编辑的值进行更新。

我的代码是：

型号：

    struct WalletItem: Identifiable{

        let id = UUID()
        var name:String
        var cardNumber:String
        var type:String
        var cvc:String
        let pin:String
        var dateOfExpiry:String
    }

ModelView：

    class Wallet: ObservableObject{

        @Published var wallets = [
            WalletItem(name: "BSB", cardNumber: "123456789", type: "master card", cvc: "1234", pin: "1234", dateOfExpiry: "2016-06-29"),
            WalletItem(name: "Alpha bank", cardNumber: "123456789", type: "master card", cvc: "1234", pin: "1234", dateOfExpiry: "2017-03-12"),
            WalletItem(name: "MTБ", cardNumber: "123456789", type: "master card", cvc: "1234", pin: "1234", dateOfExpiry: "2020-11-12"),
        ]

    }

第一视图：

    struct WalletListView: View {

        // Properties
        // ==========

        @ObservedObject var wallet = Wallet()
        @State var isNewItemSheetIsVisible = false


        var body: some View {
            NavigationView {
                List(wallet.wallets) { walletItem in
                    NavigationLink(destination: EditWalletItem(walletItem: walletItem)){
                            Text(walletItem.name)
                        }
                }
                .navigationBarTitle("Cards", displayMode: .inline)
                .navigationBarItems(
                    leading: Button(action: { self.isNewItemSheetIsVisible = true
                    }) {
                        HStack {
                            Image(systemName: "plus.circle.fill")
                            Text("Add item")
                        }
                    }
                )
            }
            .sheet(isPresented: $isNewItemSheetIsVisible) {
                NewWalletItem(wallet: self.wallet)
            }
        } 

    }

和辅助视图：

    struct EditWalletItem: View {

        @State var walletItem: WalletItem


        @Environment(\.presentationMode) var presentationMode

        var body: some View {
            Form{
                Section(header: Text("Card Name")){
                    TextField("", text: $walletItem.name)
                }

            }
            .navigationBarItems(leading:
                Button(action: {
                    self.presentationMode.wrappedValue.dismiss()
                })
                {
                    Text("Back")
                }, trailing:
                Button(action: {

                    self.presentationMode.wrappedValue.dismiss()
                })
                {
                    Text("Save")
            })

        }

    }

PS：如果我使用@Binding而不是@State，则在第一个视图中会出现错误：初始化程序init(_:)要求Binding<String>符合StringProtocol

Answer 1

这里是经过修改的部分（经过测试并可以在Xcode 11.2 / iOS 13.2上使用）：

1）确定过度绑定

struct EditWalletItem: View {
    @Binding var walletItem: WalletItem

2）通过的地方

List(Array(wallet.wallets.enumerated()), id: \.element.id) { (i, walletItem) in
    NavigationLink(destination: EditWalletItem(walletItem: self.$wallet.wallets[i])){
            Text(walletItem.name)
        }
}

Answer 2

这是approach that Asperi suggested的简化独立示例：

struct Position {
    var id = UUID()
    var count: Int
    var name: String
}

class BookingModel: ObservableObject {

    @Published var positions: [Position]

    init(positions: [Position] = []) {
        self.positions = positions
    }

}

struct EditableListExample: View {

    @ObservedObject var bookingModel: BookingModel = BookingModel(
        positions: [
            Position(count: 1, name: "Candy"),
            Position(count: 0, name: "Bread"),
        ]
    )

    var body: some View {
        // >>> Passing a binding into an Array via index:
        List(Array(bookingModel.positions.enumerated()), id: \.element.id) { i, pos in
            PositionRowView(position: self.$bookingModel.positions[i])
        }
    }
}

struct PositionRowView: View {

    @Binding var position: Position

    var body: some View {
        Stepper(
            value: $position.count,
            label: {
                Text("\(position.count)x \(position.name)")
            }
        )
    }

}

struct EditableListExample_Previews: PreviewProvider {
    static var previews: some View {
        EditableListExample()
    }
}