gistfile1.m

- (void) invalidateInContext:(NSManagedObjectContext *)context
{
    NSFetchRequest* request = [[NSFetchRequest alloc]initWithEntityName:kZODownloadName];
    
    NSPredicate* predicate = [NSPredicate predicateWithFormat:@"targetEntity == %@", self.modelClassString];
    request.predicate = predicate;
    
    NSArray* downloads = [context executeFetchRequest:request error:nil];
    
    for (ZODownload* download in downloads) {
        [context deleteObject:download];
    }    
}