I try to inject the managedObjectContext environment variable into the preview entry. Is there any difference between the two methods?

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
            // normal code            
            .environment(\.managedObjectContext, DataController.shared.container.viewContext)
            // Code that will crash
           .environment(\.managedObjectContext, DataController().container.viewContext)
    }
}

import Foundation
import CoreData

class DataController: ObservableObject {
    let container = NSPersistentContainer(name: "Bookworm")
    static let shared: DataController = DataController()

    init() {
        container.loadPersistentStores { description, error in
            if let error = error {
                print("Core Data failed to load: \(error.localizedDescription)")
            }
        }
    }
}

We can install and use the EnvInject plugin to inject environment variables during the build startup. In the build configuration window, we select the “Inject environment variables” option in the “Add build step” combo box. We can then add the required environment variables in the properties content text box.