Expand / colapse UITableViewCell

TableViewController.m

NSInteger selectedRow = -1; // default selected row (here no one)

-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    if(indexPath.row == selectedRow) {
        return 100; // expanded height
    }

    return 44; // colapsed height
}

-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [tableView deselectRowAtIndexPath:indexPath animated:YES];

    if(self.selectedRow == indexPath.row)
        selectedRow = -1;
    else
        selectedRow = indexPath.row;

    //The magic that will call height for row and animate the change in the height
    [tableView beginUpdates];
    [tableView endUpdates];
}