Board index » delphi » Checking if Datafields of type string are empty??

Andreas Vo?loh

Delphi Developer
Thu, 20 May 2004 08:01:30 GMT

Checking if Datafields of type string are empty??

Hello!

I found out, than this code causes av's later in the app, especially when
closing it.

procedure TAuftragForm.AufReTableFilterRecord(DataSet: TDataSet;
  var Accept: Boolean);
begin
  If TTable(DataSet).Active then
    Accept := (TTable(DataSet).FieldByName('LS_DT').AsString <> '') and
(TTable(DataSet).FieldByName('R_NR').AsString = '')
end;

Changing "...AsString <>/= ''" to "...AsString <>/= NULL" seems to remove
the problem.

But is this sure? And why does Delphi behave this way??

Thanks for your help,
Andreas Vo?loh

 
Manuel Algor

Delphi Developer
Thu, 20 May 2004 20:31:23 GMT

Re:Checking if Datafields of type string are empty??


FieldByName returns a variant with the value of the field, and you can
check it with IsNull, irrespective of the type of field. So I would
suggest using:

Accept:= (Not TTable(DataSet).FieldByName('LS_DT').IsNull) And (Not
TTable(DataSet).FieldByName('R_NR').IsNull);

Manuel Algora
m...@encomix.es

Andreas Vo?lo

Delphi Developer
Thu, 20 May 2004 21:02:11 GMT

Re:Checking if Datafields of type string are empty??


Ahh, thats smart... Thanks

 So I would

Quote
> suggest using:

> Accept:= (Not TTable(DataSet).FieldByName('LS_DT').IsNull) And (Not
> TTable(DataSet).FieldByName('R_NR').IsNull);

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