Easy Core Data fetching/inserting

gistfile1.m

- (void)fetchWithRequest:(NSFetchRequest *)request
  		  completion:(void(^)(NSArray *results, NSError *error))handler
{
	[request setResultType:NSManagedObjectIDResultType];
	void (^executeHandler)(NSArray *, NSError *) = ^(NSArray *results, NSError *error){
		dispatch_async(dispatch_get_main_queue(), ^{
			if (handler) handler(results, error);
		});
	};
	[self.backgroundContext performBlock:^{
		NSError *error = nil;
		NSArray *results = [self.backgroundContext executeFetchRequest:request error:&error];
		if (error) executeHandler(nil, error);
		else {
			[self.mainQueueContext performBlock:^{
				NSArray *objects = [self _transformBackgroundObjectIDsToMainQueueObjects:results];
				executeHandler(objects, nil);
			}];
		}
	}];
}

- (void)createObjectOfEntityName:(NSString *)entityName
					   configure:(void(^)(id object))configure
						  result:(void(^)(id object, NSError *error))result
{
	[self.backgroundContext performBlock:^{
		id object = [NSEntityDescription insertNewObjectForEntityForName:entityName
												  inManagedObjectContext:self.backgroundContext];
		if (configure) configure(object);
		__block NSError *error = nil;
		[self.backgroundContext save:&error];
		[self.mainQueueContext performBlockAndWait:^{
			[self.mainQueueContext save:&error];
		}];
		[self.backgroundContext refreshObject:object mergeChanges:NO];
		NSManagedObjectID *objectID = [object fgo_permanentObjectID];
		[self.mainQueueContext performBlock:^{
			NSError *existingError = nil;
			NSManagedObject *managedObject = [self.mainQueueContext existingObjectWithID:objectID
																				   error:&existingError];
			if (existingError)
				FGOGenericErrorLog(@"Error attempting to fetch object using the object ID. Trying a fetch request.", existingError);
			if (!managedObject) {
				NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:entityName];
				request.predicate = [NSPredicate predicateWithFormat:@"SELF == %@", object];
				request.fetchLimit = 1;
				NSArray *results = [self.mainQueueContext executeFetchRequest:request error:&error];
				managedObject = [results count] ? results[0] : nil;
			}
			if (result) result(managedObject, error);
		}];
	}];
}

- (void)fetchOrCreateObjectWithRequest:(NSFetchRequest *)request
							 configure:(void(^)(id object))configure
								result:(void(^)(id object, NSError *error))result
{
	request.fetchLimit = 1;
	[self fetchWithRequest:request completion:^(NSArray *results, NSError *error) {
		if (results.count) {
			if (result) result(results[0], error);
		} else {
			[self createObjectOfEntityName:request.entityName configure:configure result:result];
		}
	}];
}