function preProcess()
 {
     $this->_id = CRM_Utils_Request::retrieve('id', 'Positive', $this, FALSE);
     require_once 'CRM/Utils/Rule.php';
     if (!CRM_Utils_Rule::positiveInteger($this->_id)) {
         CRM_Core_Error::fatal(ts('We need a valid discount ID for view'));
     }
     $this->assign('id', $this->_id);
     $defaults = array();
     $params = array('id' => $this->_id);
     require_once 'CRM/CiviDiscount/BAO/Item.php';
     CRM_CiviDiscount_BAO_Item::retrieve($params, $defaults);
     require_once 'CRM/CiviDiscount/BAO/Track.php';
     $rows = CRM_CiviDiscount_BAO_Track::getUsageByCode($this->_id);
     $this->assign('rows', $rows);
     $this->assign('code_details', $defaults);
     CRM_Utils_System::setTitle($defaults['code']);
 }