How to use EnvironmentObject in app file in SwiftUI

Question

Is it possible to use EnvironmentObject in the app file for a new SwiftUI 2.0 project?
I'm using the following code and I get the error:

Fatal error: No ObservableObject of type Authentication found. A View.environmentObject(_:) for Authentication may be missing as an ancestor of this view.: file SwiftUI, line 0

I'm assuming this error is because I haven't used the .environmentObject modifier in any view yet and so the UserAuth has not yet been placed in the environment.

But I want this loginStatus to be available anywhere in my app and to be able to use the function getLoginStatus also anywhere in my app on one common instance of the UserAuth Class.

I was hoping to put this in my rootView and have it apply to all views but not sure how to do this with the structure I have below in my app file.

enum LoginStatus {
    case signedIn
    case signedOut
}

import SwiftUI

@main
struct ExampleApp: App {

    @EnvironmentObject var userAuth: UserAuth

    init() {
        userAuth.getLoginStatus()
    }
    
    var body: some Scene {
        WindowGroup {
            switch userAuth.loginStatus {
            case .signedIn:
                Text("Signed In")
            case .signedOut:
                Text("Signed Out")
            }
        }
    }
}

import SwiftUI

class UserAuth: ObservableObject {
    
    @Published var loginStatus: LoginStatus = .undetermined
    
    func getLoginStatus() {
        // asynchrounously set loginStatus
    }
}

For that why don't you make Singleton class to access your data from anywhere in App to whole lifecycle. — Kudos
– Kudos, Commented Mar 25, 2021 at 7:55

Martijn Pieters · Accepted Answer · 2022-08-23 15:08:00Z

6

You can use it as regular property at that level and pass as environment down into view hierarchy if/when needed, like

struct ExampleApp: App {

    let userAuth = UserAuth()     // << here !!
    
    var body: some Scene {
        WindowGroup {
            switch userAuth.loginStatus {
            case .signedIn:
                ContentView()
                   .environmentObject(userAuth)    // << here !!
            case .signedOut:
                Text("Signed Out")
            }
        }
    }
}

edited Aug 23, 2022 at 15:08

Martijn Pieters

1.1m326 gold badges4.2k silver badges3.4k bronze badges

answered Mar 25, 2021 at 7:37

Asperi

262k28 gold badges594 silver badges888 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

alionthego Over a year ago

the problem with this approach is that I would need to pass it around to all the other views to make it global with I really don't want to do if I can avoid that. I want there to be only one instance of this class or else the loginStatus variable wouldn't make sense.

Asperi Over a year ago

1) The instance is the only one because it is, as you see, at App level. 2) Injecting it via environmentObject(userAuth) make that instance available for all sub-view hierarchy, if you have many views inside WindowGroup just move its content into separated view and inject environment object to that one view (which is most usually is a root ContentView).

alionthego Over a year ago

I see. that makes sense and I'm very anxious to get it working. my only problem with this now is that app does not observe changes to the loginStatus var in userAuth. Is there anyway to make that happen?

alionthego Over a year ago

can I change let userAuth = UserAuth() to @ObservedObject var userAuth = UserAuth()

alionthego Over a year ago

it seems that works. I've changed it to ObservedObject in the app file and everything works very well. thanks very much for the explanation

|

Tushar Sharma · Accepted Answer · 2021-03-25 07:40:31Z

1

You need to inject UserAuth from root view, and access your object in View with @EnvironmentObject property.

import SwiftUI

@main
struct ExampleApp: App {

    var body: some Scene {
        WindowGroup {
            MainView().environmentObject(UserAuth())
        }
    }
}


class UserAuth: ObservableObject {
    
    @Published var loginStatus: LoginStatus = .undetermined
    
    func getLoginStatus() {
        // asynchrounously set loginStatus
    }
    
    enum LoginStatus {
        case undetermined
    }
}

struct MainView:View{
    var body: some View{
        Text("")
    }
}

struct MainView1:View{
    
    @EnvironmentObject var userAuth: UserAuth
    
    var body: some View{
        Text("")
    }
}

answered Mar 25, 2021 at 7:40

Tushar Sharma

2,8921 gold badge20 silver badges39 bronze badges

1 Comment

alionthego Over a year ago

I'm familiar with this approach and mentioned it in the question. I can add the environmentObject to any other view. I just want to know if there is a way to add it to the WindowGroup or somehow make it available to all views in the app. In the above structure there are basically two main views. One for the signed in fork and one for the not signed in fork. Using your approach the main view is one fork.

Collectives™ on Stack Overflow

How to use EnvironmentObject in app file in SwiftUI

2 Answers 2

6 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related