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Day 73: Challenge - Purple Error: Publishing changes from within view updates is not allowed, this will cause undefined behavior.

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Hello,

I have finished Day 72 Challanges and my code runs. However when running simulator I get "Publishing changes from within view updates is not allowed, this will cause undefined behavior." error. I think it is similar to error that Paul explains in "Locking our UI behind Face ID" topic. I have tried to use Task { @MainActor in however could not manage to get rid of those purple errors.

Is there anyway to eliminate them or should I just ignore them? You can find my Editview and EditViewModel code below. Other parts are same as Paul shows.

import SwiftUI

struct EditView: View {
    @Environment(\.dismiss) var dismiss

    @StateObject private var editViewModel : EditViewModel

    var onSave: (Location) -> Void

    var body: some View {
        NavigationView {
            Form {
                Section {
                    TextField("Place name", text: $editViewModel.name)
                    TextField("Description", text: $editViewModel.description)
                }
                Section("Nearby…") {
                    switch editViewModel.loadingState {
                    case .loaded:
                        ForEach(editViewModel.pages, id: \.pageid) { page in
                            Text(page.title)
                                .font(.headline)
                            + Text(": ") +
                            Text(page.description)
                                .italic()
                        }
                    case .loading:
                        Text("Loading…")
                    case .failed:
                        Text("Please try again later.")
                    }
                }
            }
            .navigationTitle("Place details")
            .toolbar {
                Button("Save") {
                    let newLocation = editViewModel.savePlaceInfo()
                    onSave(newLocation)
                    dismiss()
                }
                .task { 
                    await editViewModel.fetchNearbyPlaces()
                }
            }
        }
    }

    init(location: Location, onSave: @escaping (Location) -> Void) {
        _editViewModel = StateObject(wrappedValue: EditViewModel(location: location))
        self.onSave = onSave
    }

}

struct EditView_Previews: PreviewProvider {
    static var previews: some View {
        EditView(location: Location.example) { newLocation in }
    }
}
import Foundation

extension EditView {
    @MainActor
    class EditViewModel : ObservableObject {

        @Published var location : Location

        @Published var name: String
        @Published var description: String

        @Published var loadingState = LoadingState.loading
        @Published var pages = [Page]()
        enum LoadingState {
            case loading, loaded, failed
        }

        init(location: Location) {
            self.location = location

            _name = Published(initialValue: location.name)
            _description = Published(initialValue: location.description)
        }

        func savePlaceInfo() -> Location {

            var newLocation = location
            newLocation.id = UUID()
            newLocation.name = name
            newLocation.description = description

            return newLocation
        }

        func fetchNearbyPlaces() async {

            let urlString = "https://en.wikipedia.org/w/api.php?ggscoord=\(location.coordinate.latitude)%7C\(location.coordinate.longitude)&action=query&prop=coordinates%7Cpageimages%7Cpageterms&colimit=50&piprop=thumbnail&pithumbsize=500&pilimit=50&wbptterms=description&generator=geosearch&ggsradius=10000&ggslimit=50&format=json"

            guard let url = URL(string: urlString) else {
                print("Bad URL: \(urlString)")
                return
            }
                do {
                    let (data, _) = try await URLSession.shared.data(from: url)

                    // we got some data back!
                    let items = try JSONDecoder().decode(Result.self, from: data)

                    // success – convert the array values to our pages array
                    pages = items.query.pages.values.sorted()
                    loadingState = .loaded
                } catch {
                    // if we're still here it means the request failed somehow
                    loadingState = .failed
                }
        }
    }
}

Thanks,

3      

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