RestKit sync service, advice with temporary objects - How - ios

Question

I'm making some app and I want to provide offline functionality to it.
Problem is with getting new data from backend as temporary objects not saved in persistent store. Why I want this? Because I want to check whether data from backend is newer than offline one (by update date) If yes then update, otherwise, send it to the backend.
For now I'm trying something like this:
NSMutableURLRequest *apiEmailRequest = [[RKObjectManager sharedManager] requestWithObject:#"ApiEmail" method:RKRequestMethodGET path:pathToContent parameters:nil];
RKObjectRequestOperation *apiEmailOperation = [[RKObjectManager sharedManager] managedObjectRequestOperationWithRequest:apiEmailRequest managedObjectContext:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
*********************CHECK FOR BACKEND EMAILS AND OFFLINE ONE **********************
NSArray *backendEmails = [mappingResult array];
for (ApiEmail *backendEmail in backendEmails) {
if ([backendEmail isKindOfClass:[ApiEmail class]]) {
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:#"ApiEmail"];
NSPredicate *filterByApplication = [NSPredicate
predicateWithFormat:#"emailId == %#", backendEmail.emailId];
[fetchRequest setPredicate:filterByApplication];
NSArray *persistentEmails = [[RKManagedObjectStore defaultStore].persistentStoreManagedObjectContext executeFetchRequest:fetchRequest error:nil];
*HERE PUT IT INTO mainQueueManagedObjectContext and
saveToPersistentStore else POST it to the backend*
}
}
} failure:^(RKObjectRequestOperation *operation, NSError *error) {
*ERROR*
}];
return apiEmailOperation;
[[RKObjectManager sharedManager] enqueueObjectRequestOperation:apiEmailOperation];
Is there any way to do it without creating new RKObjectManager?
Best regards, Adrian.
UPDATE
-(void)willSave {
[super willSave];
NSDictionary *remoteCommits = [NSDictionary dictionaryWithDictionary:[self committedValuesForKeys:#[#"updateDate"]]];
NSDate *updateDate = [remoteCommits valueForKey:#"updateDate"];
NSComparisonResult result = [self.updateDate compare:updateDate];
if(result == NSOrderedDescending) {
[self.managedObjectContext refreshObject:self mergeChanges:NO];
} else {
[self.managedObjectContext refreshObject:self mergeChanges:YES];
}
}
After such modification I'm getting Failed to process pending changes before save. The context is still dirty after 1000 attempts.

Answer 1

The below is unlikely to work in your situation actually, specifically because of the way discardsInvalidObjectsOnInsert works.
You may be able to do this by following the below process but additionally implementing willSave on the managed object and checking the status there. If you decide to abandon the updates you can try using refreshObject:mergeChanges: with a merge flag of NO.
With KVC validation you have 2 options:
edit individual pieces of data as it is imported
abandon the import for a whole object
Option 2. requires that you use the Core Data validation to prevent the import. That means doing something like making the date stamp on the object non-optional (i.e. required) and in your KVC validation setting it to nil when you determine that the import should be aborted.
Note that for this to work you need to set discardsInvalidObjectsOnInsert on the entity mapping.

Answer 2

After big help from #Wain, I finally got it working. Without this brave men I would still be in the sandbox. Solution:
-(BOOL)validateUpdateDate:(id *)ioValue error:(NSError **)outError {
NSComparisonResult result = [self.updateDate compare:(NSDate *)*ioValue];
if (result == NSOrderedDescending) {
self.updateDate = nil;
return NO;
}
return YES;
}
-(void)willSave {
[super willSave];
if (self.updateDate == nil) {
[self.managedObjectContext refreshObject:self mergeChanges:NO];
}
}
Thank You so much for your time and help.
Best regards, Adrian.