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POUnderstanding how NSFetchedResultsController works
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copied!<p>First off, thank you very much if you find time to help me!</p> <p>I have been learning about <code>NSFetchedResultsController</code>and im trying to understand it as much as i can, however, some things about it very much confuse me. This code if from a tutorial i've found online. Basically i have the simplest fetched controller set up with really fancy methods like this</p> <pre><code>- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller { // The fetch controller is about to start sending change notifications, so prepare the table view for updates. [self.tableView beginUpdates]; } - (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:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath]; break; case NSFetchedResultsChangeMove: [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade]; // Reloading the section inserts a new row and ensures that titles are updated appropriately. [tableView reloadSections:[NSIndexSet indexSetWithIndex:newIndexPath.section] withRowAnimation:UITableViewRowAnimationFade]; break; } } (NSFetchedResultsController *)fetchedResultsController { if (_fetchedResultsController != nil) { return _fetchedResultsController; } NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"FailedBankInfo" inManagedObjectContext:_context]; [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:_context sectionNameKeyPath:nil cacheName:@"Root"]; self.fetchedResultsController = theFetchedResultsController; _fetchedResultsController.delegate = self; [sort release]; [fetchRequest release]; [theFetchedResultsController release]; return _fetchedResultsController; } </code></pre> <ol> <li><p>Do i need to create a new fetched controller everytime for different view controllers? For instance if i have a list of businesses in one list view. then i click on one of them and brings me to a list of employees in that ocmpany, i have to use a different fetchedViewController since i need to respecify the entity key right? See above my implementation. </p></li> <li><p>With my current implementation, it works great for listing items. Let's say I have a view controller called VC. init i fully implemented <code>NSFetchedResultsController</code>. I have a barbutton add item and a method called <code>addButtonPressed</code> which when pressed modally adds a view (from bottom up). In this same method i have <code>Entity myEntity = [NSEntityDescription insertNNewObjectForEntityForName:@"Entity" inManagedObjectContext:context_];</code> Then i tell the code the go into another view. <strong>HOWEVER</strong>, when the animation is moving the new navigation controller up, the new cell already shows itself mid animation. From my understanding this these two methods <code>- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath</code> <strong>AND</strong> <code>- (UITableViewCell *)tableView:(UITableView *)tableView</code> get called in conjuction with the top two methods in the code snippet above. how can i fix it? i dont want anything showing up on the current view until i added a new Entity by going to another view. The second another object gets called into the context, the update methods must get called or something</p></li> <li><p>What does this snippet of code do? Particularly the part with id < stuff ></p> <p>(void)controller:(NSFetchedResultsController *)controller didChangeSection:(id NSFetchedResultsSectionInfo)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {</p> <pre><code>switch(type) { case NSFetchedResultsChangeInsert: [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade]; break; case NSFetchedResultsChangeDelete: [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade]; break; } </code></pre> <p>} Edit: Holy $#$, formatting this frustrating. there should be didChangeSection:(id (LESS THAN EQUAL SIGN) NSFetchedResultsSectionInfo (GREATER THEN EQUAL SIGN)) in the code above</p></li> </ol> <p>4 Where can i learn more about this. i.e what the individual content updating methods do and when they are called etc. Also Does the NSFetchedResultcontroller act as a single array? Meaning that if i want to have a tableview with multiple sections i need more ViewControllers? Once again THANKS! </p>

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