我正在尝试通过构建一个作业管理应用程序来自学核心数据。我的代码构建良好,并且该应用程序可以正常运行,直到我尝试向列表中添加新任务。我Thread 1: EXC_BREAKPOINT (code=1, subcode=0x1c25719e8)在以下行中收到此错误:ForEach(courses, id: \.self) { course in。控制台也有此错误:Context in environment is not connected to a persistent store coordinator: <NSManagedObjectContext: 0x2823cb3a0>。
Thread 1: EXC_BREAKPOINT (code=1, subcode=0x1c25719e8)
ForEach(courses, id: \.self) { course in
Context in environment is not connected to a persistent store coordinator: <NSManagedObjectContext: 0x2823cb3a0>
我对Core Data知之甚少,对可能的问题不知所措。我已经在数据模型中设置了“分配”和“课程”实体,其中Course与“分配”具有一对多关系。每个作业将根据特定课程进行分类。
这是用于向列表添加新分配的视图的代码:
struct NewAssignmentView: View { @Environment(\.presentationMode) var presentationMode @Environment(\.managedObjectContext) var moc @FetchRequest(entity: Course.entity(), sortDescriptors: []) var courses: FetchedResults<Course> @State var name = "" @State var hasDueDate = false @State var dueDate = Date() @State var course = Course() var body: some View { NavigationView { Form { TextField("Assignment Name", text: $name) Section { Picker("Course", selection: $course) { ForEach(courses, id: \.self) { course in Text("\(course.name ?? "")").foregroundColor(course.color) } } } Section { Toggle(isOn: $hasDueDate.animation()) { Text("Due Date") } if hasDueDate { DatePicker(selection: $dueDate, displayedComponents: .date, label: { Text("Set Date:") }) } } } .navigationBarTitle("New Assignment", displayMode: .inline) .navigationBarItems(leading: Button(action: { self.presentationMode.wrappedValue.dismiss() }, label: { Text("Cancel") }), trailing: Button(action: { let newAssignment = Assignment(context: self.moc) newAssignment.name = self.name newAssignment.hasDueDate = self.hasDueDate newAssignment.dueDate = self.dueDate newAssignment.statusString = Status.incomplete.rawValue newAssignment.course = self.course self.presentationMode.wrappedValue.dismiss() }, label: { Text("Add").bold() })) } } }
编辑:这是AppDelegate中设置持久性容器的代码:
lazy var persistentContainer: NSPersistentCloudKitContainer = { let container = NSPersistentCloudKitContainer(name: "test") container.loadPersistentStores(completionHandler: { (storeDescription, error) in if let error = error as NSError? { fatalError("Unresolved error \(error), \(error.userInfo)") } }) return container }()
还有SceneDelegate中设置环境的代码:
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) { // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`. // If using a storyboard, the `window` property will automatically be initialized and attached to the scene. // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead). // Get the managed object context from the shared persistent container. let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext // Create the SwiftUI view and set the context as the value for the managedObjectContext environment keyPath. // Add `@Environment(\.managedObjectContext)` in the views that will need the context. let contentView = ContentView().environment(\.managedObjectContext, context) // Use a UIHostingController as window root view controller. if let windowScene = scene as? UIWindowScene { let window = UIWindow(windowScene: windowScene) window.rootViewController = UIHostingController(rootView: contentView) self.window = window window.makeKeyAndVisible() } }
像moc这样的环境值仅自动传递到层次结构中的其他视图。因此,如果您显示工作表或不属于视图层次结构的任何内容,则将失去环境,并且需要像向ContentView一样将moc传递给新层次结构。检查以下代码段:
.sheet(isPresented: self.$showSheet) { SheetView() .environment(\.managedObjectContext, self.moc) }