perform new fetch in core data iphone

I am doing core data fetches using the standard code provided by Apple, it has the following statement in the beginning of the fetch method.

- (NSFetchedResultsController *)fetchedResultsController {

    if (fetchedResultsController_ != nil) {
        return fetchedResultsController_;
    }

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];

    NSEntityDescription *entity = [NSEntityDescription entityForName:self.entityName 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:self.sortFieldName ascending:YES];
    NSMutableArray *sortDescriptors = [[NSMutableArray alloc] initWithObjects:sortDescriptor, nil];

    [fetchRequest setSortDescriptors:sortDescriptors];
    if(predicate != nil)
        [fetchRequest setPredicate:predicate];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "开发者_StackOverflow中文版no sections".
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:sectionKeyName cacheName:nil];

    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    [aFetchedResultsController release];
    aFetchedResultsController = nil;
    [fetchRequest release];

    fetchRequest = nil;
    [sortDescriptor release];
    [sortDescriptors release];

    NSError *error = nil;
    if (![fetchedResultsController_ performFetch:&error]) {

    }

    return fetchedResultsController_;
}  

The first time, fetchedResultsController gets the required info. But I am setting a predicate on this result after that. So, I would like the fetch to consider my predicate the next time. If it goes in the above code, it will come out immediately because the old value is not nil.

To overcome this, after setting the predicate, I do

fetchedResultsController_ = nil;

This works ok,but is giving leaks at the fetchedResultsController as soon as the fetchRequest is allocated.

Is there a better way to re-execute the fetch or to avoid the leak?

Just add a release.

if(fetchedResultsController_){
    [fetchedResultsController_ release];
}
fetchedResultsController_ = nil;