Xcode 6 iOS 8 iCloud core data setup

Question

Has anyone got iCloud core data syncing setup on Xcode 6 and iOS 8? (hopefully this isn't a duplicate post)

Where did iCloud Core Data storage option go?

I remember Core Data had an extra storage option called Core Data storage, but now in Xcode 6 it only seems to show key-value and document storage when I enable the iCloud toggle in Xcode 6.

Background Info

• New iPad app
• Xcode 6
• Targeting minimum version iOS 7 but hoping it works for iOS 8 too? (We can set iOS 8 as minimum)
• Want to use iCloud Core Data storage instead of key-value or document storage.
• Have logged into the same Apple account in the Settings > iCloud for both Simulator and iPad device
• My provisioning profile used to code sign the app has iCloud enabled for both development and distribution (was automatically enabled by Xcode)

My Setup

So far, I don't know if I've setup Core Data iCloud correctly.

Xcode appears to have setup the iCloud containers in the iOS Developer Portal:

iCloud.com.xxxxxx.xxxxxxxx   (note: I've replaced the actual strings with xxxx here)

My Xcode 6 iCloud "services" list shows no ticks next to:

• Key-value storage
• iCloud documents
• CloudKit

Which one should we be using now since it doesn't list "core data" as a storage option?

In the "Containers" directly below the "services", it shows the following options greyed out:

• Use default container (this one ticked by default)
• Specify custom containers
• iCloud.com.xxxxxxxxxx.xxxxxxxxx (again, substituted the real identifiers with xxxx)

I can't choose any option, it seems to force me to "Use default container".

Finally, Xcode seems to show ticks for:

• Add the "iCloud" entitlement to your App ID
• Add the "iCloud containers" entitlement to your App ID
• Add the "iCloud" entitlemen to your entitlements file
• Link CloudKit.framework

So by Xcode's own automated process, it setup everything for me.

The Reference Code

OK, so I read around and notice a iCloud stack written here:

https://github.com/mluisbrown/iCloudCoreDataStack

I've taken the necessary code and tried to adapt to my Core Data manager singleton:

DataManager.h file

+ (id)sharedModel;
+ (ALAssetsLibrary *)sharedLibrary;

@property (nonatomic, readonly) NSManagedObjectContext *mainContext;
@property (nonatomic, readonly) NSPersistentStoreCoordinator *storeCoordinator;

- (NSString *)modelName;
- (NSString *)pathToModel;
- (NSString *)storeFilename;
- (NSString *)pathToLocalStore;


#pragma mark - Entity Fetching Methods -

-(NSArray *)fetchEntityOfType:(NSString *)entityType UsingPredicated:(NSPredicate *)predicate sortBy:(NSString *)sortKey ascendingOrder:(BOOL)ascendingOrder;

DataManager.m file

@property (nonatomic, strong) NSManagedObjectModel *managedObjectModel;
- (NSString *)documentsDirectory;

@end

@implementation MLSAlbumsDataModel
@synthesize managedObjectModel = _managedObjectModel;
@synthesize storeCoordinator = _storeCoordinator;
@synthesize mainContext = _mainContext;

+ (id)sharedModel {
    static MLSAlbumsDataModel *__instance = nil;
    if (__instance == nil) {
        __instance = [[MLSAlbumsDataModel alloc] init];
    }
    return __instance;
}

+ (ALAssetsLibrary *)sharedLibrary {
    static ALAssetsLibrary *__instance = nil;
    if (__instance == nil) {
        __instance = [[ALAssetsLibrary alloc] init];
    }
    return __instance;

}

- (NSString *)modelName {
    return @"Albums";
}

- (NSString *)pathToModel {
    return [[NSBundle mainBundle] pathForResource:[self modelName] ofType:@"momd"];
}

- (NSString *)storeFilename {
    return [[self modelName] stringByAppendingPathExtension:@"sqlite"];
}

- (NSString *)pathToLocalStore {
    return [[self documentsDirectory] stringByAppendingPathComponent:[self storeFilename]];
}

- (NSString *)documentsDirectory {
    NSString *documentsDirectory = nil;
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    documentsDirectory = [paths objectAtIndex:0];
    return documentsDirectory;
}

- (NSManagedObjectContext *)mainContext {
    if(_mainContext == nil) {
        _mainContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
        _mainContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy;        

        // setup persistent store coordinator

        DLog(@"SQLITE STORE PATH: %@", [self pathToLocalStore]);
        NSURL *storeURL = [NSURL fileURLWithPath:[self pathToLocalStore]];


        //_mainContext.persistentStoreCoordinator = [self storeCoordinator];

        _mainContext.persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel];



        __weak NSPersistentStoreCoordinator *psc = self.mainContext.persistentStoreCoordinator;

        // iCloud notification subscriptions
        NSNotificationCenter *dc = [NSNotificationCenter defaultCenter];
        [dc addObserver:self
               selector:@selector(storesWillChange:)
                   name:NSPersistentStoreCoordinatorStoresWillChangeNotification
                 object:psc];

        [dc addObserver:self
               selector:@selector(storesDidChange:)
                   name:NSPersistentStoreCoordinatorStoresDidChangeNotification
                 object:psc];

        [dc addObserver:self
               selector:@selector(persistentStoreDidImportUbiquitousContentChanges:)
                   name:NSPersistentStoreDidImportUbiquitousContentChangesNotification
                 object:psc];

        NSError* error;
        // the only difference in this call that makes the store an iCloud enabled store
        // is the NSPersistentStoreUbiquitousContentNameKey in options. I use "iCloudStore"
        // but you can use what you like. For a non-iCloud enabled store, I pass "nil" for options.

        // Note that the store URL is the same regardless of whether you're using iCloud or not.
        // If you create a non-iCloud enabled store, it will be created in the App's Documents directory.
        // An iCloud enabled store will be created below a directory called CoreDataUbiquitySupport
        // in your App's Documents directory
        [self.mainContext.persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                                                                           configuration:nil
                                                                            URL:storeURL
                                                                        options:@{ NSPersistentStoreUbiquitousContentNameKey : @"iCloudStore" }
                                                                          error:&error];
        if (error) {
            NSLog(@"error: %@", error);
        }

        _storeCoordinator = self.mainContext.persistentStoreCoordinator;

    }
    return _mainContext;
}

- (NSManagedObjectModel *)managedObjectModel {
    if(_managedObjectModel == nil) {
        NSURL *storeURL = [NSURL fileURLWithPath:[self pathToModel]];
        _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:storeURL];
    }
    return _managedObjectModel;
}

- (NSPersistentStoreCoordinator *)storeCoordinator {
    if (_storeCoordinator == nil) {
        // -----------------------------------------------------------------------------------------------------------------------------
        // Code moved to managed object context code above
        // -----------------------------------------------------------------------------------------------------------------------------
        /*

        DLog(@"SQLITE STORE PATH: %@", [self pathToLocalStore]);
        NSURL *storeURL = [NSURL fileURLWithPath:[self pathToLocalStore]];

        NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

        NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                                 [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
        NSError *error = nil;




        if (![psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {
            NSDictionary *userInfo = [NSDictionary dictionaryWithObject:error forKey:NSUnderlyingErrorKey];
            NSString *reason = @"Could not create persistent store";
            NSException *exc = [NSException exceptionWithName:NSInternalInconsistencyException reason:reason userInfo:userInfo];
            @throw exc;
        }

        _storeCoordinator = psc;

         */

    }
    return _storeCoordinator;
}


#pragma mark - iCloud Related Methods -

// Subscribe to NSPersistentStoreDidImportUbiquitousContentChangesNotification
- (void)persistentStoreDidImportUbiquitousContentChanges:(NSNotification*)note
{
    NSLog(@"%s", __PRETTY_FUNCTION__);
    NSLog(@"%@", note.userInfo.description);

    NSManagedObjectContext *moc = self.mainContext;
    [moc performBlock:^{
        [moc mergeChangesFromContextDidSaveNotification:note];

        DLog(@"NSPersistentStoreDidImportUbiquitousContentChangesNotification executed");
        /*

        // you may want to post a notification here so that which ever part of your app
        // needs to can react appropriately to what was merged.
        // An exmaple of how to iterate over what was merged follows, although I wouldn't
        // recommend doing it here. Better handle it in a delegate or use notifications.
        // Note that the notification contains NSManagedObjectIDs
        // and not NSManagedObjects.
        NSDictionary *changes = note.userInfo;
        NSMutableSet *allChanges = [NSMutableSet new];
        [allChanges unionSet:changes[NSInsertedObjectsKey]];
        [allChanges unionSet:changes[NSUpdatedObjectsKey]];
        [allChanges unionSet:changes[NSDeletedObjectsKey]];

        for (NSManagedObjectID *objID in allChanges) {
            // do whatever you need to with the NSManagedObjectID
            // you can retrieve the object from with [moc objectWithID:objID]
        }

        */

    }];
}

// Subscribe to NSPersistentStoreCoordinatorStoresWillChangeNotification
// most likely to be called if the user enables / disables iCloud
// (either globally, or just for your app) or if the user changes
// iCloud accounts.
- (void)storesWillChange:(NSNotification *)note {
    NSManagedObjectContext *moc = self.mainContext;
    [moc performBlockAndWait:^{
        NSError *error = nil;
        if ([moc hasChanges]) {
            [moc save:&error];
        }

        [moc reset];
    }];

    // now reset your UI to be prepared for a totally different
    // set of data (eg, popToRootViewControllerAnimated:)
    // but don't load any new data yet.

    [[NSNotificationCenter defaultCenter] postNotificationName:@"notifCoreDataStoreWillChange" object:nil];

    DLog(@"storeWillChange notification fire");
}

// Subscribe to NSPersistentStoreCoordinatorStoresDidChangeNotification
- (void)storesDidChange:(NSNotification *)note
{
    // here is when you can refresh your UI and
    // load new data from the new store


    [[NSNotificationCenter defaultCenter] postNotificationName:@"notifCoreDataStoreDidChange" object:nil];

    DLog(@"storeDidChange notification fire");
}



#pragma mark - Entity Fetching Methods -

-(NSArray *)fetchEntityOfType:(NSString *)entityType UsingPredicated:(NSPredicate *)predicate sortBy:(NSString *)sortKey ascendingOrder:(BOOL)ascendingOrder
{
    NSEntityDescription *entityDescription = [NSEntityDescription entityForName:entityType inManagedObjectContext:[[MLSAlbumsDataModel sharedModel] mainContext]];


    NSSortDescriptor *sortDescriptor = nil;

    if(sortKey)
    {
        sortDescriptor = [[NSSortDescriptor alloc] initWithKey:sortKey ascending:ascendingOrder];
    }
    else
    {
        sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"updatedAt" ascending:ascendingOrder];
    }


    NSFetchRequest *request = [[NSFetchRequest alloc] init];

    request.entity = entityDescription;

    if(predicate)
    {
        request.predicate = predicate;
    }

    request.sortDescriptors = @[sortDescriptor];

    NSError *error = nil;

    NSArray *results = [[[MLSAlbumsDataModel sharedModel] mainContext] executeFetchRequest:request error:&error];

    if(results == nil)
    {
        DLog(@"Error getting entity of type '%@' using predicate '%@', sortKey '%@' ascendingOrder %d", entityType, predicate, sortKey, ascendingOrder);
    }

    return results;
}

My Observations

I tried to run the app on the iPad Simulator (I believe it is the iOS 8 simulator) and on iPad device running iOS 7.x

I created an album with a user entered name on the simulator, but I am not seeing the iPad device showing the newly created album. I also tried reversing the roles, iPad device create, iOS simulator no results either.

I do see my log messages:

storeDidChange notification fire

SQLITE STORE PATH: /Users/xxxxxxx/Library/Developer/CoreSimulator/Devices/3DC17576-92E9-4EAF-B77A-41340AE28F92/data/Containers/Data/Application/E51085CE-3772-4DF1-A503-1C243497091A/Documents/Albums.sqlite

If I minimise the app in the simulator and open it again (without pressing the Stop button in Xcode), I see these message:

-[PFUbiquitySwitchboardEntryMetadata setUseLocalStorage:](808): CoreData: Ubiquity:  nobody~sim301AE3E8-16B2-5A08-917D-7B55D1879BE4:iCloudStore
Using local storage: 1

I read that "Using local storage: 0" is what it should ideally be? and that 1 means local device data store rather than iCloud data store.

When I create an album, save it, stop the simulator, then start the app again, my albums disappears, but immediately after I create a new album, all the previous album reappear magically again. It's a bit odd. If I don't use iCloud and revert my code to previous setup, I can create and see my album fine, regardless of whether I minimise my app or not, or restart app, but then I don't have iCloud sync which I need.

Have I made any mistakes anywhere?

Sorry for the long post but has anyone got iCloud working for iOS 8 and Xcode 6 ?

I could really use some help.

Extra Questions

1) Does iOS 8 require the use of this container identifier ? (which Xcode 6 generated for me):

com.apple.developer.icloud-container-identifiers

That's not what the iOS 7 one looks like right? iOS 7 one is more like:

com.apple.developer.ubiquity-container-identifiers

2) Do I need an iCloud Drive account before it works?

Super confused @_@

Solution 1

iOS 8 Solution:

OK...then....lol. I think I solved it.

New discovery. After skimming through this page:

http://www.tuaw.com/2014/09/17/psa-do-not-upgrade-to-icloud-drive-during-ios-8-installation/

It says:

iCloud Drive is Apple's new and improved iCloud syncing and file storage feature that allows you to share documents between your iOS 8 devices and your Mac running OS X 10 Yosemite.

So, I decided to bite the bullet and upgrade my iCloud account to iCloud drive (free to upgrade).

After upgrading to iCloud drive, and re-ran my app with a few Xcode 6 changes, it's working now.

Some Important Things to note:

• iCloud Drive is incompatible with previous iCloud Document & Data storage. So if you're going to test, make sure all your devices are using iCloud drive and iOS 8.
• Simulator only seems to sync once, after launching app while device continuously syncs every interval. Not sure if it's a simulator bug or not. Or maybe my configuration is not perfect.
• Using "Use default containers" doesn't work in the simulator for me (but on the device it does work) on the first try, maybe need to delete the previous copy of the app and reinstall. Try using default containers first and see if it works, otherwise, read the next point below.

• For the above reason, I changed to using a Ubiquity container with this pattern:

  iCloud.$(CFBundleIdentifier)

So something like:

iCloud.com.xxxxxxxx.iCloudCoreDataDemo

Where "xxxxxxxx" is my company name identifier.

I made the above iCloud container by logging into my iOS Developer Center, perhaps you could just press the "+" sign inside Xcode 6 and enter one there, Xcode should automagically setup everything for you.

One block of code I used to test to see if it's working is this:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    self.persistentStack = [[PersistentStack alloc] initWithStoreURL:self.storeURL modelURL:self.modelURL];
    self.managedObjectContext = self.persistentStack.managedObjectContext;

    NSURL *containerURL = [[NSFileManager defaultManager] URLForUbiquityContainerIdentifier:@"iCloud.com.xxxxxxxxxx.iCloudCoreDataDemo"];

    if(containerURL == nil)
    {
        NSLog(@"containerURL == nil");
    }
    else
    {
        NSLog(@"hurray?");
    }

    return YES;
}

If you see "hurray?" then it's fine, you should also see this pattern of text in your Xcode console output:

2014-10-07 17:37:23.196 iCloudCoreDataDemo[8104:130250] documentsDirectory = file:///Users/xxxxxxxx/Library/Developer/CoreSimulator/Devices/9FAFE881-13CA-4608-8BE6-728C793FAFFB/data/Containers/Data/Application/BC6CA07D-605A-4927-94AF-E9E21E204D2B/Documents/
2014-10-07 17:37:23.386 iCloudCoreDataDemo[8104:130250] storeDidChange
2014-10-07 17:37:23.390 iCloudCoreDataDemo[8104:130250] -[PFUbiquitySwitchboardEntryMetadata setUseLocalStorage:](808): CoreData: Ubiquity:  nobody~sim301AE3E8-16B2-5A08-917D-7B55D1879BE4:iCloudStore
Using local storage: 1
2014-10-07 17:37:23.402 iCloudCoreDataDemo[8104:130250] hurray?
2014-10-07 17:37:33.909 iCloudCoreDataDemo[8104:130250] storeWillChange
2014-10-07 17:37:33.933 iCloudCoreDataDemo[8104:130250] storeDidChange
2014-10-07 17:37:33.933 iCloudCoreDataDemo[8104:130330] -[PFUbiquitySwitchboardEntryMetadata setUseLocalStorage:](808): CoreData: Ubiquity:  nobody~sim301AE3E8-16B2-5A08-917D-7B55D1879BE4:iCloudStore
Using local storage: 0

Notice the two important lines:

Using local storage: 1

later becomes:

Using local storage: 0

Local storage 1 means it's currently using local storage, while local storage 0 means it has moved the data to iCloud storage.

I hope this benefits everyone else.

iOS 7 Only Solution:

OK, so I've just discovered something and managed to get it working for iOS 7 only. I still haven't figured out how to do it in iOS 8 but I have noticed something important.

On my iPhone 5 running iOS 8.0.2, I don't have the "Document & Data" option inside the iCloud settings menu anymore.

However, on my iPad running iOS 7, I DO see the "Document & Data" options.

Perhaps this is the reason why it doesn't work on iOS 8, we no longer have Document & Data storage ?

Anyhow, here's what I discovered for iOS 7 only solution.

I found this page here

https://developer.apple.com/library/ios/documentation/General/Conceptual/iCloudDesignGuide/Chapters/iCloudFundametals.html

and one of the line says:

• iCloud document storage is for user-visible file-based content, Core Data storage, or for other complex file-based content.

Sure enough, I went into my Xcode 6 project file and ticked the "iCloud Documents" option. This un-greyed the radio buttons, but I still left it at "Use default Containers".

One thing I learned is that I need to init my PersistentStack in the appDelegate. Previously, I tried to init the persistent stack inside the +(id)sharedInstance method but it caused the iCloud to only sync the first time, so after initial load and sync, adding new record doesn't get synced afterwards.

I rewrote a basic app and modified the persistent stack slightly:

App Delegate.h

#import <UIKit/UIKit.h>
#import "PersistentStack.h"

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@property (nonatomic, strong) NSManagedObjectContext* managedObjectContext;
@property (nonatomic, strong) PersistentStack* persistentStack;


@end

App Delegate.m

@interface AppDelegate ()

@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    self.persistentStack = [[PersistentStack alloc] initWithStoreURL:self.storeURL modelURL:self.modelURL];
    self.managedObjectContext = self.persistentStack.managedObjectContext;

    return YES;
}

...

- (NSURL*)storeURL
{
    NSURL* documentsDirectory = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:NULL];
    return [documentsDirectory URLByAppendingPathComponent:@"MyApp.sqlite"];
}

- (NSURL*)modelURL
{
    return [[NSBundle mainBundle] URLForResource:@"MyApp" withExtension:@"momd"];
}

Persistent Stack.h

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>

#import "Book.h"
#import <UIKit/UIKit.h>

@interface PersistentStack : NSObject

+(id)sharedInstance;

- (id)initWithStoreURL:(NSURL *)storeURL modelURL:(NSURL *)modelURL;

@property (nonatomic,strong,readonly) NSManagedObjectContext *managedObjectContext;

#pragma mark - Regular Methods -

-(Book *)insertNewBookWithDate:(NSDate *)newDate;
-(void)deleteBook:(Book *)book;
-(NSArray *)fetchEntityOfType:(NSString *)entityType withPredicate:(NSPredicate *)predicate andSortKey:(NSString *)sortKey;

@end

Persistent Stack.m

#import "PersistentStack.h"
#import "AppDelegate.h"

@interface PersistentStack ()

@property (nonatomic,strong,readwrite) NSManagedObjectContext* managedObjectContext;
@property (nonatomic,strong) NSURL* modelURL;
@property (nonatomic,strong) NSURL* storeURL;

@end

@implementation PersistentStack

+(id)sharedInstance
{
    static PersistentStack *sharedInstance = nil;

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{

        AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;

        sharedInstance = appDelegate.persistentStack;
    });

    return sharedInstance;
}

- (id)initWithStoreURL:(NSURL*)storeURL modelURL:(NSURL*)modelURL
{
    self = [super init];
    if (self) {
        self.storeURL = storeURL;
        self.modelURL = modelURL;
        [self setupManagedObjectContext];
    }
    return self;
}

- (void)setupManagedObjectContext
{
    self.managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
    self.managedObjectContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy;
    self.managedObjectContext.persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel];


    //__weak NSPersistentStoreCoordinator *psc = self.managedObjectContext.persistentStoreCoordinator;

    // iCloud notification subscriptions
    NSNotificationCenter *dc = [NSNotificationCenter defaultCenter];
    [dc addObserver:self
           selector:@selector(storesWillChange:)
               name:NSPersistentStoreCoordinatorStoresWillChangeNotification
             object:self.managedObjectContext.persistentStoreCoordinator];

    [dc addObserver:self
           selector:@selector(storesDidChange:)
               name:NSPersistentStoreCoordinatorStoresDidChangeNotification
             object:self.managedObjectContext.persistentStoreCoordinator];

    [dc addObserver:self
           selector:@selector(persistentStoreDidImportUbiquitousContentChanges:)
               name:NSPersistentStoreDidImportUbiquitousContentChangesNotification
             object:self.managedObjectContext.persistentStoreCoordinator];

    NSError* error;
    // the only difference in this call that makes the store an iCloud enabled store
    // is the NSPersistentStoreUbiquitousContentNameKey in options. I use "iCloudStore"
    // but you can use what you like. For a non-iCloud enabled store, I pass "nil" for options.

    // Note that the store URL is the same regardless of whether you're using iCloud or not.
    // If you create a non-iCloud enabled store, it will be created in the App's Documents directory.
    // An iCloud enabled store will be created below a directory called CoreDataUbiquitySupport
    // in your App's Documents directory
    [self.managedObjectContext.persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                                                                       configuration:nil
                                                                                 URL:self.storeURL
                                                                             options:@{ NSPersistentStoreUbiquitousContentNameKey : @"iCloudStore" }
                                                                               error:&error];
    if (error) {
        NSLog(@"error: %@", error);
    }
}

- (NSManagedObjectModel*)managedObjectModel
{
    return [[NSManagedObjectModel alloc] initWithContentsOfURL:self.modelURL];
}

// Subscribe to NSPersistentStoreDidImportUbiquitousContentChangesNotification
- (void)persistentStoreDidImportUbiquitousContentChanges:(NSNotification*)note
{
    NSLog(@"%s", __PRETTY_FUNCTION__);
    NSLog(@"%@", note.userInfo.description);

    NSManagedObjectContext *moc = self.managedObjectContext;
    [moc performBlock:^{
        [moc mergeChangesFromContextDidSaveNotification:note];

        [[NSNotificationCenter defaultCenter] postNotificationName:@"notifiCloudStoreDidChange" object:nil];

        /*
        // you may want to post a notification here so that which ever part of your app
        // needs to can react appropriately to what was merged.
        // An exmaple of how to iterate over what was merged follows, although I wouldn't
        // recommend doing it here. Better handle it in a delegate or use notifications.
        // Note that the notification contains NSManagedObjectIDs
        // and not NSManagedObjects.
        NSDictionary *changes = note.userInfo;
        NSMutableSet *allChanges = [NSMutableSet new];
        [allChanges unionSet:changes[NSInsertedObjectsKey]];
        [allChanges unionSet:changes[NSUpdatedObjectsKey]];
        [allChanges unionSet:changes[NSDeletedObjectsKey]];

        for (NSManagedObjectID *objID in allChanges) {
            // do whatever you need to with the NSManagedObjectID
            // you can retrieve the object from with [moc objectWithID:objID]
        }
         */

    }];
}

// Subscribe to NSPersistentStoreCoordinatorStoresWillChangeNotification
// most likely to be called if the user enables / disables iCloud
// (either globally, or just for your app) or if the user changes
// iCloud accounts.
- (void)storesWillChange:(NSNotification *)note {

    NSLog(@"storeWillChange");

    NSManagedObjectContext *moc = self.managedObjectContext;

    //[moc performBlockAndWait:^{
    [moc performBlock:^{
        NSError *error = nil;
        if ([moc hasChanges]) {
            [moc save:&error];
        }

        [moc reset];
    }];

    // now reset your UI to be prepared for a totally different
    // set of data (eg, popToRootViewControllerAnimated:)
    // but don't load any new data yet.
}

// Subscribe to NSPersistentStoreCoordinatorStoresDidChangeNotification
- (void)storesDidChange:(NSNotification *)note {
    // here is when you can refresh your UI and
    // load new data from the new store

    NSLog(@"storeDidChange");

    [[NSNotificationCenter defaultCenter] postNotificationName:@"notifiCloudStoreDidChange" object:nil];
}

#pragma mark - Regular Methods -

-(Book *)insertNewBookWithDate:(NSDate *)newDate
{
    Book *newBook = [NSEntityDescription insertNewObjectForEntityForName:@"Book" inManagedObjectContext:self.managedObjectContext];

    newBook.bookName = @"Book";
    newBook.publishDate = newDate;

    [self.managedObjectContext save:nil];

    return newBook;
}

-(void)deleteBook:(Book *)book
{
    [self.managedObjectContext deleteObject:book];

    [self.managedObjectContext save:nil];
}

-(NSArray *)fetchEntityOfType:(NSString *)entityType withPredicate:(NSPredicate *)predicate andSortKey:(NSString *)sortKey
{
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:entityType inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];
    // Specify criteria for filtering which objects to fetch
    [fetchRequest setPredicate:predicate];
    // Specify how the fetched objects should be sorted
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:sortKey
                                                                   ascending:YES];
    [fetchRequest setSortDescriptors:[NSArray arrayWithObjects:sortDescriptor, nil]];

    NSError *error = nil;
    NSArray *fetchedObjects = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];

    if (fetchedObjects == nil)
    {
        NSLog(@"couldn't fetch entity of type '%@', error: %@", entityType, error.localizedDescription);
    }

    return fetchedObjects;
}

@end

Solution 2

I struggled with a similar issue. I would see:

Using local storage: 1

but no other output. And if I rebuilt the app I would get something like:

Error adding store for new account:

One thing to note is that I would only get this output if I first presses the "home button" on the iPhone, and then reopened the app.

A key thing to note is that I had no services selected. To fix this issue, I selected "iCloud Documents".

You may need to delete the app before rebuilding.

Comments

[Stian Høiland]

Documentation for -URLForUbiquityContainerIdentifier: Important Do not call this method from your app’s main thread. Because this method might take a nontrivial amount of time to set up iCloud and return the requested URL, you should always call it from a secondary thread. To determine if iCloud is available, especially at launch time, check the value of the ubiquityIdentityToken property instead.

[EmilyJ]

So if you have a mixture of users who have converted to iCloud Drive and who have not converted to iCloud, will a single app be able to handle both scenarios?

[Zhang]

I don't have a solid answer for that @EmilyJ but from what it appears, Apple is forcing everyone onto the new iCloud Drive. I don't know if the old method can coexist with the new method. Chances look slim. I think at the very least, you'd have to maintain a number if-else checks to see if users are using less than iOS 8 (iOS 5, iOS 6, iOS 7) vs greater than or equal to iOS 8.

[EmilyJ]

You were right on iOS 8 needed to use iCloud drive for the CoreData to work. Previously (iOS 7) one could use developer.icloud.com to see CoreData transaction files. But with iCloud Drive, the container won't show up in that site anymore. Do you know another site to see those CoreData activities?

[David]

@EmilyJ Have you noticed the Debug Navigator (during run) with iCloud tab in the column. It gives data for iCloud storage and transfer.

[sarunw]

@Zhang do you use iCloud + Core Data sync on production? Can I have your opinion on using it? Any problem so far?

[Zhang]

I haven't used Core Data + iCloud ever since the old days, didn't have any client apps that required it. Most of our data were stored on a central server and we were building data driven apps. Sorry, can't help you there @sarunw