Need to create (local) snapshots

[NorbNorb]

Is this possible:

1. snapshot the local store and then upload it to a save place
2. download it back, swap the local store with it and then rebuild iCloud from the local store?

I need a way to enable my users to keep snapshots over a long time. I have a complex data model and therefor exporting and importing the data using a custom file format is no solution to me. The complexity would be to high, esp. with schema changes.

[lhunath]

Sure, you can save the sqlite store. Then you can import it into the local or the cloud store using USM's

- (BOOL)migrateStore:(NSURL *)migrationStoreURL withOptions:(NSDictionary *)migrationStoreOptions
             toStore:(NSURL *)targetStoreURL withOptions:(NSDictionary *)targetStoreOptions
            strategy:(UbiquityStoreMigrationStrategy)migrationStrategy
               error:(__autoreleasing NSError **)outError cause:(UbiquityStoreErrorCause *)cause context:(__autoreleasing id *)context;

[NorbNorb]

Dear Maarten, sorry to ask again, but could you please comment on my approach of creating and restoring snapshots? I want to delete both locally and in iCloud if iCloud is enabled, locally only otherwise. Is this the way your API is intended to be used? I had to do a little workaround for a restoration after a deletion (see below).

Creation:

- (void)snapshotPersistentStoreToPath:(NSString *)localCopyPath
{
    [appDelegate.managedObjectContext.persistentStoreCoordinator lock];

    NSArray *stores = appDelegate.managedObjectContext.persistentStoreCoordinator.persistentStores;
    for (NSPersistentStore *store in stores)
    {
        NSURL *storeURL = [appDelegate.managedObjectContext.persistentStoreCoordinator URLForPersistentStore:store];
        NSString *storeFileName = [storeURL lastPathComponent];
        NSURL *dstFileURL = [[NSURL fileURLWithPath:localCopyPath] URLByAppendingPathComponent:storeFileName];
        // Remove Write Ahead Log (wal)
        NSDictionary *options = @{
                                  NSPersistentStoreRemoveUbiquitousMetadataOption: @YES,
                                  NSSQLitePragmasOption : @{ @"journal_mode" : @"DELETE" }
                                  };
        NSError *error;
        NSPersistentStore *storeCopy = [appDelegate.managedObjectContext.persistentStoreCoordinator migratePersistentStore:store
                                                                                                                     toURL:dstFileURL
                                                                                                                   options:options
                                                                                                                  withType:NSSQLiteStoreType
                                                                                                                     error:&error];
        if (error)
        {
            NSLog(@"%@", [error localizedDescription]);
        }

        if (storeCopy)
        {
            [appDelegate.managedObjectContext.persistentStoreCoordinator removePersistentStore:storeCopy error:&error];
        }
    }

    [appDelegate.managedObjectContext.persistentStoreCoordinator unlock];
}

Restoring: I have had the problem that right after a call to deleteCloudContainerLocalOnly: or deleteLocalStore, I could not directly start the migration from the backup store. ubiquityStoreManager:willLoadStoreIsCloud: gets called twice and I had to make sure the recovering migration happens not until the second run (that's what the variable migrateStoreAfterDeletion is for).

- (void)restoreFromPersistentStore:(NSURL *)url
{
    if (!url)
    {
        NSLog(@"Didn't get an URL to restore from.");
        return;
    }

    storeURLToMigrateFrom = url;
    migrateStoreAfterDeletion = NO;

   if (self.ubiquityStoreManager.cloudEnabled)
   {
       [self.ubiquityStoreManager deleteCloudContainerLocalOnly:NO];
   }
   else
   {
       [self.ubiquityStoreManager deleteLocalStore];
   }
}

- (void)ubiquityStoreManager:(UbiquityStoreManager *)manager willLoadStoreIsCloud:(BOOL)isCloudStore
{
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    [managedObjectContext performBlockAndWait:^{
        NSError *error = nil;
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error])
            NSLog( @"Unresolved error: %@\n%@", error, [error userInfo] );

        [managedObjectContext reset];
    }];

    _managedObjectContext = nil;

    if (storeURLToMigrateFrom)
    {
        if (!migrateStoreAfterDeletion)
        {
            migrateStoreAfterDeletion = YES;
        }
        else
        {
            NSURL *dstStoreURL = manager.cloudEnabled ? manager.URLForCloudStore : manager.URLForLocalStore;
            NSError *error;
            UbiquityStoreErrorCause cause;
            id context;
            [manager migrateStore:storeURLToMigrateFrom withOptions:nil
                          toStore:dstStoreURL withOptions:nil
                         strategy:UbiquityStoreMigrationStrategyIOS
                            error:&error
                            cause:&cause
                          context:&context];
            storeURLToMigrateFrom = nil;
            migrateStoreAfterDeletion = NO;
        }
    }
}

[lhunath]

Why do you delete the store first?

[NorbNorb]

I want to overwrite the local store or cloud container with the Core Data snapshot. And I need to get the delegate method ubiquityStoreManager:willLoadStoreIsCloud: called somehow. What's your recommendation?

[NorbNorb]

Hi lhunath, do you have a recommendation on how to handle the restoration locally / to iCloud correctly?

[lhunath]

It seems to me the best way would be to migrate the snapshot to USM's local store and then do a -migrateLocalToCloud if you want a cloud store too, or just a -deleteCloudStoreLocalOnly:NO and let USM migrate the cloud store from the local store automatically when the user turns on cloud.

[NorbNorb]

Ok, thanks, I'll do it that way. So you've asked why I delete the store first. Is there a better way than mine? As I said, I need USM to call ubiquityStoreManager:willLoadStoreIsCloud:, so I can start the migration.

[lhunath]

It will do that whenever you change the store. Eg. just a -reloadStore will trigger that.

On 23 January 2014 08:56, NorbNorb notifications@github.com wrote:

Ok, thanks, I'll do it that way. So you've asked why I delete the store first. Is there a better way than mine? As I said, I need USM to call ubiquityStoreManager:willLoadStoreIsCloud:, so I can start the migration.

— Reply to this email directly or view it on GitHubhttps://github.com/lhunath/UbiquityStoreManager/issues/46#issuecomment-33125312 .

Maarten Billemont (lhunath) me: http://www.lhunath.com – business: http://www.lyndir.com – http://masterpasswordapp.com

[ChristianRo]

Hi,

i want to achieve something similar. i´ve tried it as Ihunath described it:

• After downloading the snapshot i told usm to reload its store with reloadStore.
• As mentioned it triggers the ubiquityStoreManager:willLoadStoreIsCloud:
• in ubiquityStoreManager:willLoadStoreIsCloud: i call manager migrateStore:

but in this line i get the following error: "UbiquityStoreManager: Error (cause:UbiquityStoreErrorCauseSeedStore): Error Domain=NSCocoaErrorDomain Code=134080 "The operation couldn’t be completed. (Cocoa error 134080.)" UserInfo=0xd382770 {NSUnderlyingException=Can't add the same store twice} "

So what i´m doing wrong here? Thank you

[ChristianRo]

Hi lhunath,

could you please post a small example which shows how to use the migrateStorewithOptions Method to replace the actual store with another backup store.

Thank you for your effords.