watchOS 2 with Core Data

Question

With watchOS 1, my understanding is that the watch extension was placed in the iOS app and so you could use a shared Core Data persistent store for both the watch app and the iOS app(Which was done by using an app group, and making a separate framework that handled the data model for both the iOS app and watch app.)

However, with watchOS 2, the watch extension has moved onto the watch itself - so it would have its own persistent store.So,according to me, I can use core data on apple watch directly without using iOS app, But when I creating a project for watchOS 2 , there is no option to use core data in your watch app.If I am adding these functions in ExtensionDelegate:

lazy var applicationDocumentsDirectory: NSURL = {
    // The directory the application uses to store the Core Data store file. This code uses a directory named "finoit.test" in the application's documents Application Support directory.
    let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
    return urls[urls.count-1]
}()

lazy var managedObjectModel: NSManagedObjectModel = {
    // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
    let modelURL = NSBundle.mainBundle().URLForResource("test", withExtension: "momd")!
    return NSManagedObjectModel(contentsOfURL: modelURL)!
}()

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
    // The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added 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.
    // Create the coordinator and store
    let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("SingleViewCoreData.sqlite")
    var failureReason = "There was an error creating or loading the application's saved data."
    do {
        try coordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
    } catch {
        // Report any error we got.
        var dict = [String: AnyObject]()
        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
        dict[NSLocalizedFailureReasonErrorKey] = failureReason

        dict[NSUnderlyingErrorKey] = error as NSError
        let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
        // Replace this with code to handle the error appropriately.
        // abort() 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.
        NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
        abort()
    }

    return coordinator
}()

lazy var managedObjectContext: NSManagedObjectContext = {
    // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
    let coordinator = self.persistentStoreCoordinator
    var managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
    managedObjectContext.persistentStoreCoordinator = coordinator
    return managedObjectContext
}()

// MARK: - Core Data Saving support

func saveContext () {
    if managedObjectContext.hasChanges {
        do {
            try managedObjectContext.save()
        } catch {
            // Replace this implementation with code to handle the error appropriately.
            // abort() 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
            NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
            abort()
        }
    }
}

These functions will never call, there is any other way to use core data on apple watch?

Or Am I on wrong track in concept of apple watchOS 2 with core data?

Thanks for any advice.

please check out this link http://stackoverflow.com/questions/30834078/using-core-data-with-watchos-2-0 — Michael Wang, Sep 18 '15 at 06:55

score 5 · Answer 1 · answered Sep 18 '15 at 14:23

5

You can most certainly use CoreData with watchOS 2 (two of my apps are doing this). The option to add CoreData when you are creating the target is just a convenience checkbox that Apple hasn't added yet. You will need to manually add the functions you mentioned above and make sure to call them yourself, but it will work the same way as if it was in an iOS app.

Keep in mind that this data will not sync between the watchOS and iOS CoreData stores though, so if you want that you will need to sync the data yourself using Watch Connectivity.

answered Sep 18 '15 at 14:23

lehn0058

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Does watch kit 2.0 actually run Core Data locally on the watch? That seems very heavyweight. I thought Apple was trying to keep the code and data that runs on the watch to a minimum to conserve battery and memory. – Duncan C Sep 18 '15 at 14:36
1

Yes, watchkit 2.0 can definitely run CoreData locally on the watch. It is certainly overkill for most apps, but it will be quite beneficial for some that contain historical data. It is up to the developer to make sure they use it when appropriate. – lehn0058 Sep 18 '15 at 14:57

watchOS 2 with Core Data

1 Answers1