creating calculated field at runtime?

[koadam]

Hi,

Can someone show me how can I create a calculated field at runtime with a TOracleDataSet?
The sql is constructed also at runtime, so I *have to create the calc field at runtime, too.
I tried the following code:
f:=TIntegerField.Create(ods1);
f.FieldName:='blabla';
f.FieldKind:=fkCalculated;
f.DataSet:=ods1;
f.Name := f.Dataset.Name + f.FieldName;
ods1.FieldDefs.Add(f.name, f.DataType, f.Size, f.Required);
ods1.Open;
And seen no calc field, only the real fields...

Thanks in advance (for any info),
Koadam

 

[Marco Kalter]

I'm not sure if this is possible. You can always perform the calculation in the SQL of course. If the dataset is updatable, set TOracleDataSet.OracleDictionary.FieldKinds to True, and TOracleDataSet.RefreshOptions to [roAfterInsert, roAfterUpdate], so that the calculated fields are read-only and automatically refreshed after posting a record.

------------------
Marco Kalter
Allround Automations

 

[jpickup]

I could not believe the 'I don't know if this is possible' as in Delphi, anything possible at design-time is also possible at run-time.

So, created a project with an OracleSession, OracleDataSource, DataSet and DBGrid.

Added the following to a button and it works (is identical to the code initially posted except the FieldDefs.Add call was not necessary but also does no harm):

procedure TForm1.Button1Click(Sender: TObject);
var
fld : TIntegerField;
begin
OracleDataSet1.Close;

fld:=TIntegerField.Create(OracleDataSet1);
fld.FieldName:='blabla';
fld.FieldKind:=fkCalculated;
fld.DataSet:=OracleDataSet1;
fld.Name := fld.Dataset.Name + fld.FieldName;
fld.OnGetText := TestGetText;
OracleDataSet1.Open;
end;

 

[koadam]

yes, it works.
**But if you look at your dbgrid, the only field shown in the grid is the "blabla" field.
That's my problem

 

[jpickup]

The problem is with the Fields set up in the OracleDataSet. If no fields are setup then you see all from the query BUT as soon as you define a field (in this case the calculated one) then only those defined are seen.

So, since you are adding a field you will need to add other other fields that you want to see in the grid.

 

[koadam]

yes, that right. But, The problem is that you can add field only to a closed/inactive dataset. So, before opening the query I know nothing about the fields after opening.