How to appropriately performFetch from NSFetchedResultsController after changes in another context? - ios

Question

When I make some changes in another top layer controller with own context then I post notification to UITableViewController class for update cells. This notification calls performFetch after setting fetchedResultsController to nil. But I have seen this changes only if I reload UITableViewController entirely. I'm not using cache.
How to refresh tableView cells immediately after updating my PersistentStore?
- (void)performFetch {
NSError *error = nil;
_fetchedResultsController = nil;
if (![self.fetchedResultsController performFetch:&error]) {
NSLog(#"Unable to perform fetch. Reason: %#", [error localizedDescription]);
}
[self.tableView reloadData];
}
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController) {
return _fetchedResultsController;
} else {
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Item" inManagedObjectContext:self.managedObjectContext];
NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:#"orderingValue" ascending:YES];
[request setSortDescriptors:#[sort]];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"syncStatus != %d", ObjectDeleted];
[request setEntity:entity];
[request setFetchBatchSize:20];
[request setPredicate:predicate];
NSFetchedResultsController *fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
_fetchedResultsController = fetchedResultsController;
_fetchedResultsController.delegate = self;
}
return _fetchedResultsController;
}
UPDATED:
This is FetchedResultsController Delegate method:
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:(ItemCell *)[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
break;
}
}
Context of UITableViewController:
self.managedObjectContext = [[CoreDataController sharedInstance] newManagedObjectContext];
Context of DetailsViewController:
self.managedObjectContext = [[CoreDataController sharedInstance] masterManagedObjectContext];
CoreDataController:
- (NSManagedObjectContext *)masterManagedObjectContext {
if (_masterManagedObjectContext != nil) {
return _masterManagedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
_masterManagedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
[_masterManagedObjectContext performBlockAndWait:^{
[_masterManagedObjectContext setPersistentStoreCoordinator:coordinator];
}];
}
return _masterManagedObjectContext;
}
- (NSManagedObjectContext *)newManagedObjectContext {
NSManagedObjectContext *newContext = nil;
NSManagedObjectContext *masterContext = [self masterManagedObjectContext];
if (masterContext != nil) {
newContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
[newContext performBlockAndWait:^{
[newContext setParentContext:masterContext];
}];
}
return newContext;
}

Answer 1

I am not sure what your complete setup involves but you do need to implement NSFetchedResultsControllerDelegate protocol methods to dynamically update your tableview cells. https://developer.apple.com/library/prerelease/ios/documentation/CoreData/Reference/NSFetchedResultsControllerDelegate_Protocol/index.html
If you are using different managed object context to make updates, you will have to merge those changes as well before they are reflected in your context.
Update1
[[NSNotificationCenter defaultCenter]
addObserverForName:NSManagedObjectContextDidSaveNotification
object:nil
queue:nil
usingBlock:^(NSNotification* note) {
NSManagedObjectContext *moc = self.managedObjectContext;
if (note.object != moc) {
[moc performBlock:^(){
[moc mergeChangesFromContextDidSaveNotification:note];
}];
}
}];
Update2
You can use the following template for NSFetchedResultsControllerDelegate
#pragma mark - NSFetchedResultsControllerDelegate
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller
didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex
forChangeType:(NSFetchedResultsChangeType)type
{
switch(type)
{
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
default:
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller
didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath
forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
switch(type)
{
case NSFetchedResultsChangeInsert:
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self.tableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeMove:
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView endUpdates];
}