核心数据 + CloudKit - iOS 和 watchOS 配套应用之间的共享答案

【问题标题】：Core data + CloudKit - sharing between iOS and watchOS companion app核心数据 + CloudKit - iOS 和 watchOS 配套应用之间的共享
【发布时间】：2020-03-13 07:07:28
【问题描述】：

在我的应用程序中，我将数据与核心数据一起存储。最近我发现了 Apple 在 WWDC19 中引入的新功能，它允许核心数据与 CloudKit 一起使用。我刚刚为我的应用程序启用了 cloudKit 并使用了 NSPersistentCloudKitContainer 而不是 NSPersistentContainer 并且一切都设置好了！我所有的数据都在 ios 设备之间共享。这与 NSPersistentContainer 类似，但它在 icloud 服务器上发送更改副本，因此始终存在本地数据缓存。

现在我想从我的 Apple Watch 配套应用程序中访问该数据，但不是所有数据，只是一个特定实体！那我怎么能这样做呢？我尝试使用属性检查器设置两个目标之间共享的 NSPersistentCloudKitContainer ，但看不到任何数据。我可以在 cloudKit 仪表板中看到来自 watchOS 的请求，但 watch 没有得到任何数据。

但如果我将手表中的实体保存到核心数据中，我只能从手表中获取它。我的结论是两者都没有将数据存储在同一个地方。那么我该如何解决呢？已经在使用相同的 NSPersistendCloudKitContainer。

两个目标之间共享的容器：

import Foundation
import CoreData

public class CoreDataContainer {
    lazy var persistentContainer: NSPersistentContainer = {
        /*
         The persistent container for the application. This implementation
         creates and returns a container, having loaded the store for the
         application to it. This property is optional since there are legitimate
         error conditions that could cause the creation of the store to fail.
         */
        let container = NSPersistentCloudKitContainer(name: "MyProjectName")
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

                /*
                 Typical reasons for an error here include:
                 * The parent directory does not exist, cannot be created, or disallows writing.
                 * The persistent store is not accessible, due to permissions or data protection when the device is locked.
                 * The device is out of space.
                 * The store could not be migrated to the current model version.
                 Check the error message to determine what the actual problem was.
                 */
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
        return container
    }()

    // MARK: - Core Data Saving support

    func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }
}

【问题讨论】：

标签： core-data uikit watchkit cloudkit xcode11

【解决方案1】：

通过将 cloudKitContainerOptions 添加到我的上下文描述中来解决，如下所示：

class CoreDataStack {
    static let persistentContainer: NSPersistentCloudKitContainer = {
        let container = NSPersistentCloudKitContainer(name: "MyProjectName")
        let description = container.persistentStoreDescriptions.first

        description?.cloudKitContainerOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: "myCloudContainerID") // HERE !

        container.loadPersistentStores(completionHandler: { (_, error) in
            if let error = error as NSError? {
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
        return container
    }()  

}

【讨论】：