NSPredicate使用功能不工作(NSPredicate With FUNCTION Not W

我断言不断崩溃我的应用程序的消息不支持的函数表达式FUNCTION(SELF, "filterDistanceWithLatitude:" , latitude, longitude ）。有谁知道如何解决这一问题？

- (void)setUpFetchedResultsController
{
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"NextTime"]; //Retrieve data for the place entity
    request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES selector:@selector(localizedCaseInsensitiveCompare:)]]; //How to sort it
    self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:self.context sectionNameKeyPath:nil cacheName:nil]; //Puts the data in a NSFetchedResultsController which is oddly located in CoreDataTableViewController //Puts the data in a NSFetchedResultsController which is oddly located in CoreDataTableViewController
    self.filtered = self.fetchedResultsController.fetchedObjects;
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"FUNCTION(self, 'filterByDistanceWithLatitude:', latitude, longtitude) > 20"];
    self.filtered = [self.filtered filteredArrayUsingPredicate:predicate];
}

- (double)filterByDistanceWithLatitude:(NSNumber *)latitude andLongitude:(NSNumber *)longitude
{
    CLLocationDegrees latitudeCoor = [latitude doubleValue]; //Puts the latitude into a NextTime object.
    CLLocationDegrees longitudeCoor = [longitude doubleValue]; //Puts the longtitude into a NextTime object.

    CLLocation *loc1 = [[CLLocation alloc] initWithLatitude:latitudeCoor longitude:longitudeCoor];
    CLLocation *loc2 = [[CLLocation alloc] initWithLatitude:self.currentLocation.latitude longitude:self.currentLocation.longitude];

    NSNumber *distance = [[NSNumber alloc] initWithDouble:[loc1 distanceFromLocation:loc2]];

    return [distance doubleValue];
}