Ans :
Use NSFetchResultsController : A controller that you use to manage the results of a Core Data fetch request and to display data to the user.
If we have very large data in database and we want all data to show in tableview, then we have to write some extra code on core data fetch request as fetching data will stuck UI.
Then we can use NSFetchResultsController as it has ability to fetch data from memory in batches. So data coming in batch when we scroll tableview and saved in cache.
We have to make property of type NSFetchResultsController :
and in ViewDidLoad :
We get data in numberOfRowInSection :
We get data in cellForRowAtIndexPath :
We also have to write FetchResultsControllerDelegate methods as it is as at apple provide at end of ViewController's code.
Enjoy lazy loading data...
Tutorial : Ray Wanderlich
Use NSFetchResultsController : A controller that you use to manage the results of a Core Data fetch request and to display data to the user.
If we have very large data in database and we want all data to show in tableview, then we have to write some extra code on core data fetch request as fetching data will stuck UI.
Then we can use NSFetchResultsController as it has ability to fetch data from memory in batches. So data coming in batch when we scroll tableview and saved in cache.
We have to make property of type NSFetchResultsController :
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:@"FailedBankInfo" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSSortDescriptor *sort = [[NSSortDescriptor alloc]
initWithKey:@"details.closeDate" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];
[fetchRequest setFetchBatchSize:20];
NSFetchedResultsController *theFetchedResultsController =
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:managedObjectContext sectionNameKeyPath:nil
cacheName:@"Root"];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;
return _fetchedResultsController;
}
and in ViewDidLoad :
- (void)viewDidLoad {
[super viewDidLoad];
NSError *error;
if (![[self fetchedResultsController] performFetch:&error]) {
// Update to handle the error appropriately.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
exit(-1); // Fail
}
self.title = @"Failed Banks";
}
We get data in numberOfRowInSection :
id sectionInfo =
[[_fetchedResultsController sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
We get data in cellForRowAtIndexPath :
FailedBankInfo *info = [_fetchedResultsController objectAtIndexPath:indexPath];
We also have to write FetchResultsControllerDelegate methods as it is as at apple provide at end of ViewController's code.
Enjoy lazy loading data...
Tutorial : Ray Wanderlich
