Cambie NSFetchedResultsController en cambio de SegmentedControl

Tengo una UITableView que se rellena con un Core Data NSFetchedResultsController . Ahora agregué un UISegmentedControl a la vista y cuando cambias el segmento actual, me gustaría cambiar el contenido de tableview.

He leído en línea que sería prudente usar dos NSFetchedResultsControllers diferentes, ya que puedo beneficiarme del almacenamiento en caching incorporado. El único problema es que no puedo encontrar ningún código de muestra para hacer esto y no sé por dónde empezar.

¿Alguien puede explicar dónde empezar a crear un segundo NSFetchedResultsController y cambiar qué fonts la tablaview se basa en el control segmentado?

Ver el código del encabezado:

 #import <CoreData/CoreData.h> @interface DomainViewController : UIViewController <NSFetchedResultsControllerDelegate, UITableViewDataSource, UITableViewDelegate> { UITableView *domainView; UISegmentedControl *segmentedControl; NSString *domain; } @property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController; @property (nonatomic, retain) NSManagedObjectContext *managedObjectContext; @property (nonatomic, retain) NSString *domain; @property (nonatomic, retain) IBOutlet UITableView *domainView; @property (nonatomic, retain) IBOutlet UISegmentedControl *segmentedControl; - (IBAction)segmentedControlIndexChanged; 

Ver código de implementación:

 @interface DomainViewController () - (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath; @end @implementation DomainViewController @synthesize fetchedResultsController = __fetchedResultsController; @synthesize managedObjectContext = __managedObjectContext; @synthesize domain; @synthesize domainView; @synthesize segmentedControl; - (void)viewDidLoad { [super viewDidLoad]; if (self.managedObjectContext == nil) { self.managedObjectContext = [(GARankingsAppDelegate *)[[UIApplication shanetworkingApplication] delegate] managedObjectContext]; } } - (IBAction)segmentedControlIndexChanged { switch(self.segmentedControl.selectedSegmentIndex){ case 0: break; case 1: break; default: break; } } - (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath { NSManagedObject *managedObject = [self.fetchedResultsController objectAtIndexPath:indexPath]; cell.textLabel.text = [[managedObject valueForKey:@"Keyphrase"] description]; } #pragma mark - Table view data source - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return [[self.fetchedResultsController sections] count]; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section]; return [sectionInfo numberOfObjects]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } // Configure the cell. [self configureCell:cell atIndexPath:indexPath]; return cell; } - (NSFetchedResultsController *)fetchedResultsController { if (__fetchedResultsController != nil) { return __fetchedResultsController; } /* Set up the fetched results controller. */ // Create the fetch request for the entity. NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; // Edit the entity name as appropriate. NSEntityDescription *entity = [NSEntityDescription entityForName:@"Result" inManagedObjectContext:self.managedObjectContext]; [fetchRequest setEntity:entity]; // Set the batch size to a suitable number. [fetchRequest setFetchBatchSize:20]; // Edit the sort key as appropriate. NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Keyphrase" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; // Edit the section name key path and cache name if appropriate. // nil for section name key path means "no sections". NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"]; aFetchedResultsController.delegate = self; self.fetchedResultsController = aFetchedResultsController; [aFetchedResultsController release]; [fetchRequest release]; [sortDescriptor release]; [sortDescriptors release]; NSError *error = nil; if (![self.fetchedResultsController performFetch:&error]) { /* Replace this implementation with code to handle the error appropriately. abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button. */ NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return __fetchedResultsController; } 

Cualquier ayuda es muy apreciada. Gracias.

ACTUALIZACIÓN: código actualizado

Ver el código del encabezado:

 @property (nonatomic, retain) NSFetchedResultsController *currentFetchedResultsController; @property (nonatomic, retain) NSFetchedResultsController *competitorFetchedResultsController; @property (nonatomic, retain) NSFetchedResultsController *keyphraseFetchedResultsController; 

Ver código de implementación:

 @synthesize currentFetchedResultsController = __fetchedResultsController; @synthesize competitorFetchedResultsController; @synthesize keyphraseFetchedResultsController; - (NSFetchedResultsController *)fetchedResultsController { if (__fetchedResultsController != nil) { return __fetchedResultsController; } /* Set up the fetched results controller. */ // Create the fetch request for the entity. NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; // Edit the entity name as appropriate. NSEntityDescription *entity = [NSEntityDescription entityForName:@"Result" inManagedObjectContext:self.managedObjectContext]; [fetchRequest setEntity:entity]; // Set the batch size to a suitable number. [fetchRequest setFetchBatchSize:20]; // Edit the sort key as appropriate. NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Keyphrase" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; // Edit the section name key path and cache name if appropriate. // nil for section name key path means "no sections". NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"]; aFetchedResultsController.delegate = self; //self.fetchedResultsController = aFetchedResultsController; self.currentFetchedResultsController = aFetchedResultsController; [aFetchedResultsController release]; [fetchRequest release]; [sortDescriptor release]; [sortDescriptors release]; NSError *error = nil; //if (![self.fetchedResultsController performFetch:&error]) if (![self.currentFetchedResultsController performFetch:&error]) { /* Replace this implementation with code to handle the error appropriately. abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button. */ NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return __fetchedResultsController; } 

Puede agregar otra variable de instancia que represente el NSFetchedResultsController actualmente seleccionado. Y cuando los cambios UISegmentedControl actualizan este ivar.

esta podría ser la acción que se activa por el evento value-change del segmento

 - (IBAction *)segmentChanged:(UISegmentedControl *)sender { if ([sender selectedSegmentIndex] == 0) { self.currentFetchedResultsController = self.nsfrc1; [self.tableView reloadData]; } else if ([sender selectedSegmentIndex] == 1) { self.currentFetchedResultsController = self.nsfrc2; [self.tableView reloadData]; } } 

un método UITableViewDataSource como ejemplo:

 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return [[self.currentFetchedResultsController sections] count]; } 

y debe asegurarse de que solo el nsfrc actual desencadene una actualización de vista de tabla en los methods NSFetchedResultsControllerDelegate. Entonces, tienes que cambiarlos a todos también.

 - (void)controllerWillChangeContent:(NSFetchedResultsController *)controller { if (controller == self.currentFetchedResultsController) { [self.tableView beginUpdates]; } } 

EDIT: No, lo estás haciendo mal. the currentFetchedResultsController es solo un ivar, sin un getter de carga perezoso. Es "simplemente" un puntero al controller actualmente utilizado.

Pero los otros dos fetchedResultsControllers deberían tener un getter de carga perezoso.

 - (NSFetchedResultsController *)competitorFetchedResultsController { if (!myCompetitorFetchedResultsController) { // create competitorFetchedResultsController } return myCompetitorFetchedResultsController; } - (NSFetchedResultsController *)keyphraseFetchedResultsController { if (!myKeyphraseFetchedResultsController) { // create keyphraseFetchedResultsController } return myKeyphraseFetchedResultsController; } 

y luego cambiar con:

 self.currentFetchedResultsController = self.keyphraseFetchedResultsController; 

o

 self.currentFetchedResultsController = self.competitorFetchedResultsController;