Setting the Core Data context on SwiftUI Preview in Xcode 12

Hi,

Previously to get the canvas working with Core Data-based apps, one had to inject the Core Data context via an environment variable into the PreviewProvider like so:

Code Block 
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
         let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
         return ContentView().environment(\.managedObjectContext, context)
     }
 }

However, in Xcode 12 we have ditched the AppDelegate for an @main-based App.

I've setup my new @main App like so:

Code Block 
@main
struct MyCoolApp: App {
    @Environment(\.scenePhase)
    private var scenePhase
    var body: some Scene {
        WindowGroup {
            ContentView()
                .frame(idealWidth: 480, idealHeight: 600)
                .environment(\.managedObjectContext, persistentContainer.viewContext)
        }
        .onChange(of: scenePhase) { (newScenePhase) in
            switch newScenePhase {
            case .background:
                saveContext()
            default:
                break
            }
        }
    }
    var persistentContainer: NSPersistentContainer = {
        let container = NSPersistentContainer(name: "MyCoolAppData")
        container.loadPersistentStores { (description, error) in
            if let error = error {
                print(error)
            }
        }
        return container
    }()
    func saveContext() {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                print(error)
            }
        }
    }
}

and created the accompanying MyCoolAppData.xcdatamodeld data model file.

How would I reference the persistentContainer from my App file, in ContentView's PreviewProvider now that you can't reference UIApplication.shared.delegate any more?

Thanks!