这就是我的代码：

struct ServicesView: View {
    @FetchRequest(entity: Category.entity(), sortDescriptors: [NSSortDescriptor(keyPath: \Category.name, ascending: false)], animation: .easeIn) var results: FetchedResults<Category>

    var body: some View {
        List(results) { category in
            VStack(alignment: .leading, spacing: 3, content: {
                Text(category.name)
                    .font(.system(size: 12))
                    .foregroundColor(.white)
                Text("x\(category.services.count)")
            })
        }
        .overlay(
            Text(results.isEmpty ? "Nothing here" : "")
        )
        .onAppear {
            print("😋")
            print(Category.numberOfEntities())
        }
    }
}

字符串
在控制台上显示：
😋
10
为什么单子上没有？

的数据
数字是如何计算的？

extension NSManagedObjectContext {
    static func defaultContext() -> NSManagedObjectContext {
        CoreDataManager.shared.defaultContext!
    }
}

protocol Fetchable {
    associatedtype FetchableType: NSManagedObject = Self
    static func numberOfEntities() -> Int
}

extension Fetchable where Self: NSManagedObject {
    static var entityName: String {
        entity().name ?? ""
    }
    static func numberOfEntities() -> Int {
        let request = NSFetchRequest<FetchableType>(entityName: entityName)
        let context = NSManagedObjectContext.defaultContext()
        do {
            return try context.count(for: request)
        } catch let error as NSError {
            print("❌ Core Data Count Error \(error), \(error.userInfo)")
            return 0
        }
    }
}

型
我想问题就在这里，因为我没有在任何地方分配@Environment’s managedObjectContext。我该怎么做？

@main
struct Watch_AppApp: App {
    var body: some Scene {
        WindowGroup {
                TabView {
                    TimerView()
                    ContentView()
                    ServicesView()  // how do I assign here managed object context?
                    Text("4th page")
                }
                .tabViewStyle(PageTabViewStyle())
                .onAppear(perform: loadData) //load data, fetch categories from cloudkit and save to core data, is is fetched and saved
            }
    }
}

型