当我的核心数据存储已从后台扩展更新时，如何刷新我的 SwiftUI 视图？

Question

我有一个带有意图扩展目标的 SwiftUI 应用程序。我还有一个位于共享应用程序组的核心数据存储。

Intents 扩展可以使用newBackgroundContext()Shortcuts 应用程序成功地将数据写入商店。我的 SwiftUI 应用程序可以从应用程序组中读取数据，viewContext但只有当我强制退出应用程序并重新打开它时。

我想我需要一种方法来让我的应用程序知道它已在不同的上下文中更新，但我不确定该怎么做？

我试过context.automaticallyMergesChangesFromParent = true在应用程序委托中设置并在 SwiftUI 视图中添加context.refreshAllObjects()，onAppear但这似乎没有任何区别。

mergeChanges(fromContextDidSave:)似乎很有希望，但我不确定如何获取通知。

我是 Core Data 的新手并且很困惑，所以任何指向正确方向的指针都会很棒，谢谢！

这是我当前代码的消毒版本：

应用委托

 lazy var persistentContainer: NSCustomPersistentContainer = {
        let container = NSCustomPersistentContainer(name: "exampleContainerName")
        container.loadPersistentStores { description, error in
            if let error = error {
                print("error loading persistent core data store")
            }
        }
        return container
    }()

    func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                print("error saving core data context")
            }
        }
    }

class NSCustomPersistentContainer: NSPersistentContainer {
    override open class func defaultDirectoryURL() -> URL {
        var storeURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: "exampleAppGroupName")
        storeURL = storeURL?.appendingPathComponent("exampleContainerName")
        return storeURL!
    }
}

场景委托

guard let context = (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer.viewContext else {
            fatalError("Unable to read managed object context.")
}

if let windowScene = scene as? UIWindowScene {
let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: ExampleView.environment(\.managedObjectContext, context))
            self.window = window
            window.makeKeyAndVisible()
}

Swift UI 视图

import SwiftUI
import CoreData

struct ExampleView: View {

    @Environment(\.managedObjectContext) var managedObjectContext
    @FetchRequest(
        entity: ExampleEntityName.entity(),
        sortDescriptors: [
            NSSortDescriptor(keyPath: \ExampleEntityName.date, ascending: false),
        ]
    ) var items: FetchedResults<ExampleEntityName>

    var body: some View {
        VStack {
            List(items, id: \.self) { item in
                Text("\(item.name)")
            }
        }
    }
}

意图扩展

class NSCustomPersistentContainer: NSPersistentContainer {
    override open class func defaultDirectoryURL() -> URL {
        var storeURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: "exampleContainerName")
        storeURL = storeURL?.appendingPathComponent("exampleAppGroupName")
        return storeURL!
     }
}

let persistentContainer: NSCustomPersistentContainer = {
    let container = NSCustomPersistentContainer(name: "exampleContainerName")
    container.loadPersistentStores { description, error in
        if let error = error {
            print("error loading persistent core data store: \(error)")
        }
    }
    return container
}()

let context = persistentContainer.newBackgroundContext()

let entity = NSEntityDescription.entity(forEntityName: "ExampleEntityName", in: context)
let newEntry = NSManagedObject(entity: entity!, insertInto: context)
newEntry.setValue(Date(), forKey: "date")
newEntry.setValue("Hello World", forKey: "name")

do {
    try context.save()
} catch {
    print("Failed saving")
}

Answer 1

class Data: ObservableObject {

    @Published var dataToUpdate: Int 
}

struct UpdateView : View {

@EnvironmentObject data: Data


   ...body ... {
     // use data.dataToUpdate here
  }
}

只需像本示例中所示定义数据即可。然后每当数据库发生更改时填充 dataToUpdate...当然这只是一个简化的示例，只有一个 Int 值...