Auto Post Packing Slip for Sales Order

private void postPackingSlip(FormDataSource salesTable_ds)
{
    salesFormLetter salesFormLetter;
    SalesTable salesTable;
    ;

    try
    {
        for (salesTable = salesTable_ds.getFirst(true) ? salesTable_ds.getFirst(true) : salesTable_ds.cursor();
         salesTable;
         salesTable = salesTable_ds.getNext())
        {
            salesFormLetter = SalesFormLetter::construct(DocumentStatus::PackingSlip);
            salesFormLetter.update(salesTable, SystemDateGet(),SalesUpdate::All, AccountOrder::None, false, false);
        }
    }
    catch(Exception::Error)
    {
        throw error(strFmt('The Sales order %1 could not be posted', salestable.SalesId));
    }
}