Core Data Persistent Store Migration

Persistent Store Migration

// for custom overwrites within an entity like changing an attribute from Boolean to NSNumber, etc
- (BOOL)createDestinationInstancesForSourceInstance:(NSManagedObject *)sInstance 
                                      entityMapping:(NSEntityMapping *)mapping 
                                            manager:(NSMigrationManager *)manager 
                                              error:(NSError **)error {
    NSManagedObject *newObject = 
        [NSEntityDescription insertNewObjectForEntityForName:[mapping destinationEntityName] 
                                      inManagedObjectContext:[manager destinationContext]];

    // do transfer of nsdate to nsstring non-lightweight operations here
    NSDate *date = [sInstance valueForKey:@"timeStamp"];
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateStyle:NSDateFormatterMediumStyle];    

    // set the value for our new object
    [newObject setValue:[dateFormatter stringFromDate:date] forKey:@"printedDate"];

    // do the coupling of old and new
    [manager associateSourceInstance:sInstance withDestinationInstance:newObject forEntityMapping:mapping];

    return YES;
}


NSArray *mappingModelNames = @[@"Business", @"Tasks", @"Forms", @"ChatMessages"];
NSDictionary *options = @{
                              NSMigratePersistentStoresAutomaticallyOption : @YES,
                              NSInferMappingModelAutomaticallyOption : @YES
                         };

NSURL *destinationStoreURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"HaptikLib.sqlite"];

for (NSString *mappingModelName in mappingModelNames) {

    NSURL *modelURL = [HPBundle URLForResource:@"Haptik" withExtension:@"momd"];

    NSMappingModel *mappingModel = [[NSMappingModel alloc] initWithContentsOfURL:fileURL];
    
    
    NSMigrationManager *manager = [[NSMigrationManager alloc] initWithSourceModel:sourceModel
                                                             destinationModel:targetModel];

    BOOL isSuccess = [migrationManager migrateStoreFromURL:sourceStoreURL
                                                      type:sourceStoreType
                                                    options:options
                                           withMappingModel:mappingModel
                                           toDestinationURL:destinationStoreURL
                                            destinationType:destinationStoreType
                                         destinationOptions:options
                                                      error:&error];
}