带有核心数据的 iOS 今日扩展

Question

I am trying to make a today extension for my ios app. That today extension will display the 'next' Course based on data saved with core data. I've been doing some research and I understand I have to share my persistentContainer with an appGroup. So I did :

• enabled appGroups for both ios app and today extension targets.
• coded a function to share it :

public extension NSPersistentContainer {
    func addToAppGroup(id: String) {
        guard let fileContainer = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: id) else {
            fatalError("Shared file container could not be created.")
        }
        let storeURL = fileContainer.appendingPathComponent("\(self.name).sqlite")
        let storeDescription = NSPersistentStoreDescription(url: storeURL)
        self.persistentStoreDescriptions.append(storeDescription)
    }
}

then in my core data stack :

internal class CoreDataContainer {

    static var persistentContainer: NSPersistentContainer = {
        let container = NSPersistentCloudKitContainer(name: "SchoolCompanion")
        container.addToAppGroup(id: "group.com.Ce-dricLoneux.School-Companion")
        container.loadPersistentStores(completionHandler: { (_, error) in
            if let error = error as NSError? {
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
        return container
    }()

    // MARK: - Core Data Saving support

    func saveContext () {
        let context = CoreDataContainer.persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }
}

that files and the xcdatamodel are shared between both targets. At this point I thought I could access my core data from my extension but when i do a fetch request I don't get any result. The controllerDidChangeContent is never executed.

class TodayViewController: UIViewController, NCWidgetProviding {
private func configureFetchedResultsController() {
        let request: NSFetchRequest<Course> = Course.fetchRequest()
        request.sortDescriptors =  []
        self.fetchedResultsController = NSFetchedResultsController<Course>(fetchRequest: request, managedObjectContext: CoreDataContainer.persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil)
        self.fetchedResultsController.delegate = self
        do {
            try self.fetchedResultsController.performFetch()
        } catch {
            print(error.localizedDescription)
        }
    }

override func viewDidLoad() {
        super.viewDidLoad()

        self.extensionContext?.widgetLargestAvailableDisplayMode = .compact
        self.configureFetchedResultsController()

    }

func widgetPerformUpdate(completionHandler: (@escaping (NCUpdateResult) -> Void)) {
        // Perform any setup necessary in order to update the view.

        // If an error is encountered, use NCUpdateResult.Failed
        // If there's no update required, use NCUpdateResult.NoData
        // If there's an update, use NCUpdateResult.NewData

        completionHandler(NCUpdateResult.newData)
    }
}

// MARK: - FetchedResultsController Delegate

extension TodayViewController: NSFetchedResultsControllerDelegate {
    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        print("content did change")
    }
}

I tried to make a fetch request direclty too, buti get an empty array as result. Why does I don't get any result ?

Another thing : i used nsfetchedResult controller in order to refresh the view data each time the data is updated from the ios app so is that ok or should I use the widgetPerformUpdate method ? In that case we don't know when the today extension will be refreshed and it may dispay outdated data.

main documentation used : https://www.avanderlee.com/swift/core-data-app-extension-data-sharing/

Answer 1

You should subclass NSPersistentCloudKitContainer like below, returning the App Group URL for defaultDirectoryURL() . Then in your CoreDataStack , use let container = GroupedPersistentCloudKitContainer(name: "SchoolCompanion") . Also remove, your call to addToAppGroup(...) . You will need to instantiate the GroupedPersistentCloudKitContainer in both the App and the Extension, you will also need to make sure the GroupedPersistentCloudKitContainer is linked to both Targets.

class GroupedPersistentCloudKitContainer: NSPersistentCloudKitContainer {

    enum URLStrings: String {
        case group = "group.com.yourCompany.yourApp"
    }


    override class func defaultDirectoryURL() -> URL {
        let url = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: URLStrings.group.rawValue)

        if !FileManager.default.fileExists(atPath: url!.path) {
            try? FileManager.default.createDirectory(at: url!, withIntermediateDirectories: true, attributes: nil)
        }
        return url!
    }
    ...
}

Answer 2

The url for your app group is here:

let url = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: "SchoolCompanion)

The sqlite-file is there. You don't need Cloud container.