使用NSPersistentCloudKitContainer的SwiftUI CloudKit公共数据库

Question

基于以下WWDC20 talk：https://developer.apple.com/videos/play/wwdc2020/10650/

用NSPersistentCloudKitContainer在“一行代码”中设置CloudKit公共数据库的方法如下：

    description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
    description.setOption(true as NSNumber, forKey:NSPersistentStoreRemoteChangeNotificationPostOptionKey)
    description.cloudKitContainerOptions?.databaseScope = .public

​

​

这在新的SwiftUI Persistent.swift模板上会是什么样子？

我尝试了下面的代码，但不起作用：

import CoreData

struct PersistenceController {
    static let shared = PersistenceController()

    static var preview: PersistenceController = {
        let result = PersistenceController(inMemory: true)
        let viewContext = result.container.viewContext
        for _ in 0..<10 {
            let newItem = Item(context: viewContext)
            newItem.timestamp = Date()
        }
        do {
            try viewContext.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)")
        }
        return result
    }()

    let container: NSPersistentCloudKitContainer
    
   //This doesnt work
    //container.cloudKitContainerOptions?.databaseScope = .public


    init(inMemory: Bool = false) {
        container = NSPersistentCloudKitContainer(name: "Market")
        if inMemory {
            container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
        }
        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)")
            }
        })
    }
}

Answer 1

guard let description = container.persistentStoreDescriptions.first else {
     print("Can't set description")
     fatalError("Error")
 }
    
 description.cloudKitContainerOptions?.databaseScope = .public