Server side script failing while using editor api.

sajil

i am trying to implement the inline edit using datatables.editor api in codeignitor.But my server side script is failing to update the data.Its throwing error "Fatal error: Call to a member function transaction() on a non-object in /media/recbackup/webserver/falcon/application/helpers/Editor/Editor.php on line 408".I think there is a problem in integrating with codeignitor.

My codes are as follows

$('#datatables').DataTable( {

    ajax: global_base_url + "contact/update_records_list_view",
    columns: [
        { data: null, defaultContent: '', orderable: false },
        { data: null, defaultContent: '', orderable: false },
        { data: null, defaultContent: '', orderable: false },
        { data: 3 },
        { data: 4 },
        { data: 5 },
        { data: 6 },
        { data: 7 },
        { data: 8 },

    ],
    order: [ 1, 'asc' ],
    tableTools: {
        sRowSelect: "os",
        sRowSelector: 'td:first-child',

    }

} );

  public function update_records_list_view()
     {
      $db= "";

     Editor::inst($db,'contact' )
     ->fields(
     Field::inst( 'email_primary',3 )->validator( 'Validate::email' ),
     Field::inst( 'contact_home',4 )->validator( 'Validate::numeric' ),
     Field::inst( 'contact_mobile',5 )->validator( 'Validate::numeric' ),
     Field::inst( 'country',6 )->validator('Validate::notEmpty'),
     Field::inst( 'unique_id',7 )->validator('Validate::notEmpty'),
     Field::inst( 'title',8 )->validator( 'Validate::numeric' )

)
->process( $_POST )
->json();
     }

I have failed to find anything after debugging of codes.Pls help.