gistfile1.m

- (NSInteger)tableView:(UITableView *)tableView
sectionForSectionIndexTitle:(NSString *)title
               atIndex:(NSInteger)index{
    NSLog(@"Touched on section %@", title);
    
    NSInteger firstStartingWithLetter = 0;
    
    // búsqueda de la primera familia cuyo nombre empieza
    // por la letra tocada
    for (NSString *familyName in self.familyNames) {
        if ([[familyName substringToIndex:1] isEqualToString:title]) {
            firstStartingWithLetter = [self.familyNames indexOfObject:familyName];
        }
    }
    
    return firstStartingWithLetter;
}