TableView is not update from a NSFetchedResultsController

- (void)tableView:(UITableView *)aTableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
	self.songListView = nil;
	COLLECTIONS *selectedObject = [[self fetchedResultsController] objectAtIndexPath:indexPath];
	NSUInteger i = [selectedObject.collectionContainSongs count] ;
	NSString * s = [NSString stringWithFormat: @\"%d\", i];
	SongTableViewController* songView = [[SongTableViewController alloc] initWithNibName:@\"SongTableViewController\" songs:selectedObject.collectionContainSongs managedcont:managedObjectContext title:selectedObject.name bundle:nil];
	self.songListView = songView;
	[songView release];
	[self.navigationController pushViewController:self.songListView animated:TRUE];
}

#import <UIKit/UIKit.h>
#import <CoreData/CoreData.h>
@class RootViewController;
@interface SongTableViewController : UITableViewController <NSFetchedResultsControllerDelegate>{
    NSFetchedResultsController *songfetchedResultsController;
    NSManagedObjectContext *managedObjectContext;
	UINavigationBar* navBar;
//@private:
	NSPredicate *songPredicate;
	//NSMutableArray* mysongs;
}
@property (nonatomic, retain) NSFetchedResultsController *songfetchedResultsController;
@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain) IBOutlet UINavigationBar* navBar;
@property (nonatomic, retain) NSMutableArray* mysongs;
@property (nonatomic, retain) NSPredicate *songPredicate;

- (id)initWithNibName:(NSString *)n songs:(NSSet*)s managedcont:(NSManagedObjectContext*) _managedObjectContext title:(NSString *)_title bundle:(NSBundle *)b;
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath ;
@end

#import \"SongTableViewController.h\"
#import \"SONGS.h\"

@implementation SongTableViewController
@synthesize navBar, mysongs, managedObjectContext, songfetchedResultsController, songPredicate;

- (id)initWithNibName:(NSString *)n songs:(NSSet*)s managedcont:(NSManagedObjectContext*) _managedObjectContext title:(NSString *)_title  bundle:(NSBundle *)b
{
	if(self = [super initWithNibName:n bundle:b])
	{
		self.managedObjectContext = _managedObjectContext;
		self.title = _title;
	}
	return self;
}

- (void)viewDidLoad {
    [super viewDidLoad];
	NSError *error = nil;
//I want to create a predicate for chosen the corresponding songs in the COLLECTION. It works fine.
	if (self.title != nil){ 
		self.songPredicate = [NSPredicate predicateWithFormat: @\"(songBelongingToCollection.name LIKE[c] %@)\", self.title];
	}
	else{
		self.songPredicate =nil;
	}
	if (![[self songfetchedResultsController] performFetch:&error]) {
		NSLog(@\"Unresolved error %@, %@\", error, [error userInfo]);
		abort();
	}
}

- (void)viewWillDisappear:(BOOL)animated {
	self.songfetchedResultsController = nil;
    [super viewWillDisappear:animated];
}
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {
    SONGS *managedObject = [self.songfetchedResultsController objectAtIndexPath:indexPath];
	NSLog(@\"The title of the song: %@\", managedObject.name);
    [cell.textLabel setText : managedObject.name] ;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    // Return the number of sections.
	NSLog([NSString stringWithFormat: @\"section :%d\", [[self.songfetchedResultsController sections] count]]);
    return [[self.songfetchedResultsController sections] count];	
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    id <NSFetchedResultsSectionInfo> sectionInfo = [[self.songfetchedResultsController sections] objectAtIndex:section];
    NSLog([NSString stringWithFormat: @\"rownum: %d\", [sectionInfo numberOfObjects]]);
	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];
    }
	[self configureCell:cell atIndexPath:indexPath];
    return cell;
}

//The most important function, I think, this is the source of the problem. 
- (NSFetchedResultsController *)songfetchedResultsController {
    if (songfetchedResultsController != nil) {
        return songfetchedResultsController;
    }
    // Create the fetch request for the entity.
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@\"SONGS\" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];
    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];
	if (self.songPredicate != nil) {//this part is always called, when the view is loaded, and it is valid.
		NSLog(@\"predicate: %@\",self.songPredicate);
		[fetchRequest setPredicate:self.songPredicate];
		self.songPredicate = nil;
	}
    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@\"name\" ascending:NO];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
    [fetchRequest setSortDescriptors:sortDescriptors];
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@\"Root\"];
    aFetchedResultsController.delegate = self;
    self.songfetchedResultsController = aFetchedResultsController;
    [aFetchedResultsController release];
    [fetchRequest release];
    [sortDescriptor release];
    [sortDescriptors release];
    return songfetchedResultsController;
}    

- (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;
    }
}

- (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];
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    [self.tableView endUpdates];
}

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        NSManagedObject *objectToDelete = [self.songfetchedResultsController objectAtIndexPath:indexPath];        
        NSManagedObjectContext *context = [self.songfetchedResultsController managedObjectContext];
        [context deleteObject:objectToDelete];
        NSError *error;
        if (![context save:&error]) {
            NSLog(@\"Unresolved error %@, %@\", error, [error userInfo]);
            abort();
        }
    }   
}
- (void)dealloc {
    [super dealloc];
	self.songPredicate = nil;
	self.songfetchedResultsController = nil;
}
@end