从列表触发时未显示SwiftUI警报

Question

我正在尝试在用户点击图像视图时显示带有一些文本的警报。图像视图是用于构建单个列表项的foreach循环的一部分。

该按钮正在工作，并且正在触发Observable对象上的更改，但是未触发警报isPresented ...这真令人困惑！

该视图嵌套在几个视图中，以简化代码。我共享了代码片段来说明我的问题。希望这对某人有意义，并且可以提出解决方案。

以下是包含的视图：

struct AssignmentsBoardView: View {
    @ObservedObject var presenter: AssignmentPresenter
    @ObservedObject var dogAlert: BookingNotesAlert = BookingNotesAlert()
    
    init(_ presenter: AssignmentPresenter) {
        self.presenter = presenter
    }
    
    var body: some View {
        VStack {
            Spacer()
            if (presenter.state == ViewState.loading) {
                LoadingIndicator(label: "Fetching collections")
            } else if (presenter.state == ViewState.complete) {
                VStack {
                    BoardDriversView(drivers: self.presenter.boardDrivers, currentDriver: self.presenter.selectedDriver, onSelected: self.changeDriver(boardDriver:))
                    AssignmentTypeHeaders(setCollections: {
                        self.changeAssignmentState(state: AssignmentState.collections)
                    }, setDropOffs: {
                        self.changeAssignmentState(state: AssignmentState.dropOffs)
                    }, currentAssignmentType: self.presenter.assignmentState)
                    ScrollView {
                        AssignmentDataView(presenter: self.presenter, dogAlert: self.dogAlert)
                    }
                }.alert(isPresented: self.$dogAlert.showAlert, content: {
                    Alert(title: Text("Booking Notes"), message: Text(self.dogAlert.getDogNotes()), dismissButton: .default(Text("Ok")))
                })
            } else {
                Text("No Assignments")
            }
            Spacer()
        }
    }
    
    private func changeDriver(boardDriver: BoardDriver) {
        self.presenter.changeSelectedDriver(driver: boardDriver)
    }
    
    private func changeAssignmentState(state: AssignmentState)  {
        self.presenter.changeAssignment(newState: state)
    }
}

struct AssignmentDataView: View {
    @ObservedObject var presenter: AssignmentPresenter
    var dogAlert: BookingNotesAlert
    
    @ViewBuilder
    var body: some View {
        if (self.presenter.assignmentState == AssignmentState.collections) {
            if (self.presenter.collections.isEmpty) {
                Text("No Collections scheduled for this driver")
            } else {
                ForEach(self.presenter.collections, id: \.id) { listItem in
                    CollectionListItem(dog: listItem, dogNotesAlert: self.dogAlert)
                }
            }
        } else {
            if (self.presenter.dropOffs.isEmpty) {
                Text("No Drop Offs scheduled for this driver")
            } else {
                ForEach(self.presenter.dropOffs, id: \.id) { listItem in
                    CollectionListItem(dog: listItem, dogNotesAlert: self.dogAlert)
                }
            }
        }
    }
}

这是可观察对象：

class BookingNotesAlert: ObservableObject {
    @Published var showAlert = false
    var dog: DogCollectionListItem? = nil
    
    func showAlert(dog: DogCollectionListItem) {
        self.dog = dog
        self.showAlert.toggle()
        print("Toggled stuff")
        print("Notes \(self.getDogNotes())")
    }
    
    func getDogNotes() -> String {
        self.dog?.bookingNotes ?? "No notes provided"
    }
}

这就是我正在消费的地方：

struct CollectionListItemThumbnail: View {
    var dog: DogCollectionListItem
    var dogNotesAlert: BookingNotesAlert
    
    var body: some View {
        Group {
            HStack {
                if (!dog.bookingNotes.isEmpty) {
                    Button(action: {
                        self.dogNotesAlert.showAlert(dog: dog)
                        print("Tapping")
                    }, label: {
                        ImageView(withUrl: dog.thumbnailUrl, 75, highlight: true)
                            .padding(.trailing, 12)
                            .padding(.bottom, 12)
                            .padding(.top, 12)
                    })
                } else {
                    ImageView(withUrl: dog.thumbnailUrl, 75)
                        .padding(.trailing, 12)
                        .padding(.bottom, 12)
                        .padding(.top, 12)
                }
            }
        }
    }
}

尝试Asperi的建议：

struct AssignmentsBoardView: View {
    @ObservedObject var presenter: AssignmentPresenter
    @State var dogAlert: BookingNotesAlert?
    
    init(_ presenter: AssignmentPresenter) {
        self.presenter = presenter
    }
    
    var body: some View {
        VStack {
            Spacer()
            if (presenter.state == ViewState.loading) {
                LoadingIndicator(label: "Fetching collections")
            } else if (presenter.state == ViewState.complete) {
                VStack {
                    BoardDriversView(drivers: self.presenter.boardDrivers, currentDriver: self.presenter.selectedDriver, onSelected: self.changeDriver(boardDriver:))
                    AssignmentTypeHeaders(setCollections: {
                        self.changeAssignmentState(state: AssignmentState.collections)
                    }, setDropOffs: {
                        self.changeAssignmentState(state: AssignmentState.dropOffs)
                    }, currentAssignmentType: self.presenter.assignmentState)
                    Button(action: {
                        let dog = self.presenter.collections[0]
                        dog.bookingNotes = "Test"
                        self.dogAlert = BookingNotesAlert(dog: dog)
                    }, label: {Text("Show booking notes")})
                    ScrollView {
                        AssignmentDataView(presenter: self.presenter, dogAlert: self.$dogAlert)
                    }
                }.alert(item: $dogAlert) { dogAlert in
                    Alert(title: Text("Booking Notes"), message: Text(dogAlert.getDogNotes()), dismissButton: .default(Text("Ok")))
                }
            } else {
                Text("No Assignments")
            }
            Spacer()
        }
    }
}

class BookingNotesAlert: Identifiable {
    var dog: DogCollectionListItem? = nil
    let id: UUID = UUID()
    
    init(dog: DogCollectionListItem) {
        self.dog = dog
        print("Item Id >> \(id)")
        print("Notes >> \(self.getDogNotes())")
    }
    
    func getDogNotes() -> String {
        self.dog?.bookingNotes ?? "No notes provided"
    }
}

这是单击按钮后的控制台日志：

    Item Id >> 6D695709-2894-4735-8DF6-81E36E1E8F4D
    Notes >> Test
    Item Id >> FB69ED3A-D462-4C08-8DD5-764C8A54A7B5
    Notes >> Test
    Item Id >> 484E0B22-F0BD-477A-8BE2-55F626F02609
    Notes >> Test
    Item Id >> F99E568F-C5BE-4B35-AEDF-E5A4A2700447
    Notes >> Test