How to inject .environmentObject() in watchOS6

Question

I want to inject an EnvironmentObject while creating a SwiftUI view in watchOS6.

But since WKHostingController expects a Concrete type I am not able to do the following ContentView().environmentObject(UserData())

class HostingController: WKHostingController<ContentView> {
    override var body: ContentView {
        return ContentView().environmentObject(UserData())
    }
}

This code fails with the following error:

Cannot convert return expression of type 'some View' to return type 'ContentView'

I have seen workaround like this : Using environmentObject in watchOS this seems like a hack instead of a proper solution.

I asked a watchOS engineer on Twitter regarding the same and his reply was to place .environmentObject(UserData()) inside the body of ContentView(). I tried doing that but Xcode reports an error.

So has anyone found a way to do the same ?

Paunchy

Answer 1

The workaround from the link uses AnyView, which is a very bad idea. It has been explained in several other questions and tweets from Apple engineers, that AnyView should only be used on leaf views, as there is a heavy performance hit otherwise.

As for the second option (put the environmentObject inside ContentView), it works fine. Here you have an example:

class UserData: ObservableObject {
    @Published var show: Bool = true
}

struct ContentView: View {
    @State var model = UserData()

    var body: some View {
        SubView().environmentObject(model)
    }
}

struct SubView: View {
    @EnvironmentObject var model: UserData

    var body: some View {
        VStack {
            Text("Tap Me!").onTapGesture {
                self.model.show.toggle()
            }

            if self.model.show {
                Text("Hello World")
            }
        }
    }
}

Hickie

Thanks ! How did you figure this out ? – Paunchy

You're welcome... how did I figure it out? I don't know... I became very familiar with SwiftUI's declaration file. I don't know how many times I've been up and down with it. Cheers. – Hickie

I tried this, and had problems with modifying the model in the ContentView not updating the view. I had to explicitly pass it as an environment object to a subview and modify it there for changes to propagate (as in this example). – Feldman