從可見(jiàn)的行列表中提取部分： NSArray *indexPathsForVisibleRows = [tableView indexPathsForVisibleRows];
NSMutableIndexSet *indexSet = [NSMutableIndexSet indexSet];
for ( NSIndexPath *indexPath in indexPathsForVisibleRows ) {
[indexSet addIndex:indexPath.section];
}
NSLog(@"indexSet %@",indexSet);
// indexSet <NSMutableIndexSet: 0x11a5c190>[number of indexes: 5 (in 1 ranges