I am new to swiftUI. I have one application in which i am making api call, in this application i want to display error if API does not return the response. When i navigate first time to the screen, it displays alert message, but when i go back to previous screen and again navigate back to same screen. alert is not displayed.

struct DashboardView: View {

@ObservedObject var viewModel = DashboardViewModel()
@State private var showingAlert = true

init() {
    UINavigationBar.appearance().titleTextAttributes = [.foregroundColor: UIColor.black]
    self.showingAlert = true
}

var body: some View {
        ZStack {
            Color.white
            if case .LOADING = viewModel.currentState {

                loaderView()
                .onAppear(perform: viewModel.getDashboardData)
            } else if case .SUCCESS(let dashboard) = viewModel.currentState {
                ScrollView(.vertical, showsIndicators: false) {
                    VStack(alignment: .leading, spacing: 10) {
                        HStack {
                            Text("Date:")
                                .foregroundColor(Color.black)
                            Text(dashboard.date)
                                .foregroundColor(Color.black)
                        }
                        VStack(alignment: .leading) {
                            Text("HDURL:")
                                .foregroundColor(Color.black)
                            Text(dashboard.hdurl)
                                .foregroundColor(Color.black)
                        }

                        HStack {
                            Text("Media Type:")
                                .foregroundColor(Color.black)
                            Text(dashboard.mediaType)
                                .foregroundColor(Color.black)
                        }
                        HStack {
                            Text("Service Version:")
                                .foregroundColor(Color.black)
                            Text(dashboard.serviceVersion)
                                .foregroundColor(Color.black)
                        }
                        VStack(alignment: .leading) {
                            Text("Title:")
                                .foregroundColor(Color.black)
                            Text(dashboard.title)
                                .foregroundColor(Color.black)
                        }
                        VStack(alignment: .leading) {
                            Text("url:")
                                .foregroundColor(Color.black)
                            Text(dashboard.url)
                                .foregroundColor(Color.black)
                        }
                        VStack(alignment: .leading) {
                            Text("Explanation:")
                                .foregroundColor(Color.black)
                            Text(dashboard.explanation)
                                .foregroundColor(Color.black)
                        }
                    }
                    .padding(.horizontal, 10)
                    .padding(.top, UIApplication.shared.keyWindow!.safeAreaInsets.top )

                }
                .padding(.top, UIApplication.shared.keyWindow!.safeAreaInsets.top )
            } else if case .FAILURE(let error) = viewModel.currentState {
                VStack {
                    Text("No Data")
                        .foregroundColor(Color.black)
                }

          
            }

        }
         .navigationBarTitle("Dashboard", displayMode: .inline)
         .alert(item: $viewModel.appError) { appAlert in
             Alert(title: Text("Error"),
                   message: Text("""
                     \(appAlert.errorString)
                     Please try again later!
                     """
                     )
             )
         }

         .ignoresSafeArea(.all)
}

}

enum ViewStateDashboard { case START case LOADING case SUCCESS(dashboardModel: Dashboard) case FAILURE(error: String) }

protocol FetchDashboardDataFromServer { func getDashboardData() var currentState: ViewStateDashboard { get set } }

class DashboardViewModel: ObservableObject, FetchDashboardDataFromServer {

struct AppError: Identifiable {
    let id = UUID().uuidString
    let errorString: String
}

@Published var appError: AppError?

let monitor = NWPathMonitor()
let monitorPostUser = NWPathMonitor()

let queue = DispatchQueue(label: "InternetConnectionMonitor")

var cancelable: Set<AnyCancellable> = []
@Published var currentState: ViewStateDashboard = .START

init() {
    self.currentState = .LOADING
}


// GET Method
func getDashboardData() {
    print("fetch dashboard data")
    self.currentState = .LOADING
    monitor.pathUpdateHandler = { pathUpdateHandler in
        if pathUpdateHandler.status == .satisfied {

            APIClient.dispatch(
                APIRouter.GetDashboardData(queryParams:
                APIParameters.GetDasbhboardParams(apikey: "bWrk8rdLvkzZG5fHgMBQfU9t0xYFdhC6jOT5UKsY")))
            .sink { completion in
                switch completion {
                case .finished:
                    print("Execution Finihsed dashboard.")
                case .failure(let error):
                    DispatchQueue.main.async {
                        print("dashboard error", error)
                        self.appError = AppError(errorString: error.localizedDescription)
                        self.currentState = .FAILURE(error: error.localizedDescription)
                    }
                }
            }
        receiveValue: {  dashboardData in
            print("received dashboard data", dashboardData)
            self.currentState = .SUCCESS(dashboardModel: dashboardData)
        }.store(in: &self.cancelable)

        } else {
            DispatchQueue.main.async {
                self.currentState = .FAILURE(error: StringConstants.NoInterNet)
                self.appError = AppError(errorString: StringConstants.NoInterNet)
                print("no internet get users")
            }
        }
    }
    monitor.start(queue: queue)

}

}

What could be the issue here? Any help would be appreciated.

CodePudding user response：

When you close the alert, viewModel.appError is set to nil. If you want it to appear again, you must set it to a value again.