在 SwiftUI 中，我可以在不在 SceneDelegate 中传递 @EnvironmentObject 吗？ 喜欢在任何视图中传递它

Question

My question is simple, since @EnvironmentObject can be used to share object between multiple view, and in almost all tutorials the @EnvironmentObject objects are all setup and passed in the SceneDelegate like this:

let userSettings = UserSettings()
let contentView = UserSettingsDemo().environmentObject(userSettings)
window.rootViewController = UIHostingController(rootView: contentView)

Can I pass my @EnvironmentObject object not in the SceneDelegate, but rather in any other View? for example in UserSettingsDemo.swift:

struct UserSettingsDemo: View {
var userSettings: UserSettings

var body: some View {
    VStack {
        //this is child view, and it may have other child views inside it, 
        //Like I said, I pass the @EnvironmentObject userSettings here as the 
        //start point, not in the SceneDelegate, so that FancyScoreView's child views
        //can use userSettings as @EnvironmentObject
        FancyScoreView().environmentObject(userSettings)
    }
}

}

Can I use @EnvironmentObject like above what I said? The reason I'm asking this question is that in lots of scenarios we couldn't or it's not feasible to pass all we think it's 'Global' to SceneDelegate. Sometimes we can only get something that need to be global in the mid way. sometimes it's even a bad practice to pass all global stuff right in the start point of the app.

Answer 1

As .environmentObject modifier returns some View , so yes, you can.

 /// Supplies an `ObservableObject` to a view subhierachy. /// /// The object can be read by any child by using `EnvironmentObject`. /// /// - Parameter bindable: the object to store and make available to /// the view's subhiearchy. @inlinable public func environmentObject<B>(_ bindable: B) -> some View where B : ObservableObject

Answer 2

struct ContentView: View {
    var settings: UserSettings

    var body: some View {
        NavigationView {
            VStack {
                // A button that writes to the environment settings
                Button(action: {
                    // Do something with settings
                }) {
                    Text("Settings")
                }

                NavigationLink(destination: DetailView().environmentObject(settings)) {
                    Text("Show Detail View")
                }
            }
        }
    }
}

struct DetailView: View {
    @EnvironmentObject var settings: UserSettings

    var body: some View {
        // A text view that reads from the environment settings
        Text("Some text")
    }
}

As you can see, we didn't need to explicitly associate the UserSettings instance in our scene delegate.

However @EnvironmentObject is used for data that should be shared with all views in your entire app. This lets us share model data, settings, theme, anywhere it's needed, while also ensuring that our views automatically stay updated when that data changes.