Core Data Objects Section 错误问题

- (NSFetchedResultsController *)fetchedResultsController { if (fetchedResultsController != nil) {return fetchedResultsController;} // Create and configure a fetch request with the plant entity.NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];NSEntityDescription *entity = [NSEntityDescription entityForName:@"RWPlant" inManagedObjectContext:managedObjectContext];[fetchRequest setEntity:entity]; // Create the sort descriptors array.        NSSortDescriptor *typeDescriptor = [[NSSortDescriptor alloc] initWithKey:@"type" ascending:YES];NSSortDescriptor *nameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:typeDescriptor, nameDescriptor, nil];[fetchRequest setSortDescriptors:sortDescriptors]; // Create and initialize the fetch results controller.NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:@"type" cacheName:@"Plants"];self.fetchedResultsController = aFetchedResultsController;fetchedResultsController.delegate = self; // Memory management.[aFetchedResultsController release];[fetchRequest release];        [categoryDescriptor release];[nameDescriptor release];[sortDescriptors release]; return fetchedResultsController;}