core data fetch

gistfile1.m

    NSString *currentChromosome = @"18";
    NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Gene"];
    NSSortDescriptor *alphaSortNameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"acronym" ascending:YES];
    NSArray *sortDescriptors = [NSArray arrayWithObject:alphaSortNameDescriptor];
    [fetchRequest setSortDescriptors:sortDescriptors];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"chromosome.identity = %@", currentChromosome];
    [fetchRequest setPredicate:predicate];
    NSError *fetchError = nil;
    NSArray *genes = [[[DataManager sharedInstance] mainObjectContext] executeFetchRequest:fetchRequest error:&fetchError];
    
    if (!fetchError)
    {
        // do stuff with the array.
        for (Gene *gene in genes)
        {
            NSLog(@"%@", gene.acronym);
        }
    }
    else {
        NSAssert(!fetchError, @"Failed to fetch data. Aborting.");
    }