SwiftUI - how to get @EnvironmentObject data inside @ObservableObject

Question

Is it possible to use a @EnvironmentObject inside an ObservableObject?

It is giving me an error:

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

I know the @EnvironmentObject is good because I use it other places.

If not, how can I get the information?

class ResultsViewModel: ObservableObject {
    @EnvironmentObject var entry: EntryViewModel
    ...
}

Thank you.

pawello2222 · Accepted Answer · 2020-08-27 23:47:37Z

7

Is it possible to use a @EnvironmentObject inside an ObservableObject?

No, it is not. @EnvironmentObject can be used in View only.

If not, how can I get the information?

A possible solution is to pass it in init:

class ResultsViewModel: ObservableObject {
    var entry: EntryViewModel

    init(entry: EntryViewModel) {
        self.entry = entry
    }
}

Another solution may be to use a singleton or (maybe the best) dependency injection.

edited Aug 27, 2020 at 23:47

answered Aug 27, 2020 at 23:18

pawello2222

55.6k23 gold badges183 silver badges240 bronze badges

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

8 Comments

diogenes Over a year ago

I tried the init() and it was a no go. caused other issues. thanks.

pawello2222 Over a year ago

@diogenes EnvironmentObject is kind of a singleton for views. If you want to have it always available you may need to use a singleton or dependency injection

diogenes Over a year ago

this is sort of over my pay grade. researching now... thanks.

SerhiiK Over a year ago

Interestingly you can use Environment in ObservableObject. Even though documentation describes Environment as "a property wrapper that reads a value from a view’s environment".

Geob Over a year ago

@SerhiiK Is that so? Please confirm :) Am running to go test.

|

malhal · Accepted Answer · 2025-01-04 11:31:22Z

6

You could go via DynamicProperty making use of its update func, e.g.

class MyObject: ObservableObject {
    var context: NSManagedObjectContext? 
}

struct MyProperty: DynamicProperty {
    @Environment(\.managedObjectContext) private var viewContext
    @StateObject var object = MyObject()

    // update is called before body in the View containing this property
    func update() {
        // environment vars now are valid

        if object.context != viewContext {
            // do something
            object.context = viewContext
        }
    }
}

struct MyView {
    var myProperty = MyProperty()

    var body: some View {
    }
}

edited Jan 4 at 11:31

answered Jun 28, 2022 at 10:19

malhal

31.5k7 gold badges125 silver badges154 bronze badges

1 Comment

aehlke Over a year ago

Any downside to this approach? I don't see it recommended much but it looks great

Collectives™ on Stack Overflow

SwiftUI - how to get @EnvironmentObject data inside @ObservableObject

2 Answers 2

8 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

8 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related