SwiftUI @EnvironmentObject error: may be missing as an ancestor of this view
Solution 1
The whole issue is very easy to fix just add self.networkManager @ EarthQuakeList.swift
.sheet(isPresented: $showEditPage) {
return EditPage().environmentObject(self.networkManager)
I got the reason and inspired from article: https://github.com/peterfriese/Swift-EnvironmentObject-Demo
Solution 2
if you are using sheet ore navigation you have to pass the environment Object maybe its a bug of swiftUI but it works for me in Xcode 11.5:
.sheet(isPresented: $show){
mySheetView().environmentObject(self.myEnviromentObject)
}
Solution 3
This problem seems to be cause by using two instances of NetworkManager
in your code.
If you add this line to the NetworkManager
:
final class NetworkManager: … {
static let shared = NetworkManager()
}
And then update the references in your two views like this:
struct EarthQuakeList: … {
@ObservedObject var networkManager = NetworkManager.shared
…
}
struct EditPage: … {
@ObservedObject var networkManager = NetworkManager.shared
…
}
This will make sure both views use the exact same object to access the information. By using the same object, updates in one view will cause the other view to be updated as well.
Once this works, I recommend to play around with .environmentObject()
(example) in SwiftUI as this would allow for sharing the same instance of these service types across your application.
Good luck with your project!
![Sky](https://i.stack.imgur.com/rzQf5.jpg?s=256&g=1)
Sky
Updated on June 08, 2022Comments
-
Sky about 2 years
my first view can get all the data from API request, then opened second view to change the API request data, it crashed.
below is the error
Fatal error: No ObservableObject of type NetworkManager found. A View.environmentObject(_:) for NetworkManager may be missing as an ancestor of this view.: file /BuildRoot/Library/Caches/com.apple.xbs/Sources/Monoceros_Sim/Monoceros-39.3/Core/EnvironmentObject.swift, line 55 2019-11-07 12:00:01.961425-0800 EarthQuake[73703:5913116] Fatal error: No ObservableObject of type NetworkManager found. A View.environmentObject(_:) for NetworkManager may be missing as an ancestor of this view.: file /BuildRoot/Library/Caches/com.apple.xbs/Sources/Monoceros_Sim/Monoceros-39.3/Core/EnvironmentObject.swift, line 55
This is swift file to fetch data from API, then save data to posts
import Foundation import Combine final class NetworkManager: ObservableObject { @Published var posts = [Post]() func fetchData() { //some code to fetch data, then save to posts } }
In my first list view file: EarthQuakeList.swift
import SwiftUI struct EarthQuakeList: View { @EnvironmentObject var networkManager: NetworkManager //@ObservedObject var networkManager = NetworkManager() var body: some View { NavigationView { List(networkManager.posts) { post in NavigationLink(destination: EarthQuakeDetail(detail: post.properties, location: post.locationCoordinate)) { ListRow(magnitude: post.properties.mag ?? 0.0, place: post.properties.place) } } .navigationBarTitle(Text("Today")) .navigationBarItems( trailing: VStack { Button(action: { print("Edit button tapped") self.showEditPage.toggle() }) { //Top right icon Image(systemName: "pencil.circle") .resizable() .frame(width: 20, height: 20, alignment: .center) }.sheet(isPresented: $showEditPage) { return EditPage().environmentObject(self.networkManager) } } ) } .onAppear { //Call function to fetch data self.networkManager.fetchData() } } }
Everything works well, I can see all the data, but when I do the same thing in my second view file, I get the data back, but it does not update for the first view
In my second editing view file: EditPage.swift
import SwiftUI struct EditPage: View { //@ObservedObject var networkManager = NetworkManager() @EnvironmentObject var networkManager: NetworkManager var body: some View { VStack { Text("Edite") } .onAppear(){ //I called the same function to get data as in first view file, but it is not updating the list view self.networkManager.fetchData() } } }
SceneDelegate.swift
import UIKit import SwiftUI class SceneDelegate: UIResponder, UIWindowSceneDelegate { var window: UIWindow? func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) { //Set up environment object let contentView = EarthQuakeList().environmentObject(NetworkManager()) // Use a UIHostingController as window root view controller. if let windowScene = scene as? UIWindowScene { let window = UIWindow(windowScene: windowScene) window.rootViewController = UIHostingController( rootView: contentView ) self.window = window window.makeKeyAndVisible() } }
So I am expecting second view file to call function self.networkManager.fetchData() to get data from API call, then update list view in first swift file EarthQuakeList, the issue is I am just getting correct data back, the view is not updating with new data