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aaa.aaaa · Guest

Hy !!!

I would like to know why the clone method of TCustomADODataSet doesn't
clone the Calculated fields

example :

.......

procedure TForm1.Button2Click(Sender: TObject);
var
msg: string;
begin
if m_ADOQuery <> nil then
FreeAndNil(m_ADOQuery);
m_ADOQuery:= TADOQuery.Create(Nil);
Self.ADOQuery1.Open;
m_ADOQuery.Clone(Self.ADOQuery1);

DataSource1.DataSet:= m_ADOQuery;

msg:= 'ADOQuery1 Field Count' + IntToStr(ADOQuery1.Fields.Count);
msg:= msg + #13#10 + 'm_ADOQuery Field Count' +
IntToStr(m_ADOQuery.Fields.Count);
msg:= msg + #13#10 + 'ADOQuery1 FieldDefList Count' +
IntToStr(ADOQuery1.FieldDefList.Count);
msg:= msg + #13#10 + 'm_ADOQuery FieldDefList Count' +
IntToStr(m_ADOQuery.FieldDefList.Count);

MessageDlg(msg, mtInformation, [mbOK], 0); DataSource1.DataSet:= nil;

end;

The Calculated fields are not cloned how can i clone them ?

Thanks

Here bellow a part of the .dfm file

object ADOQuery1: TADOQuery
Connection = ADOConnection1
CursorType = ctStatic
OnCalcFields = ADOQuery1CalcFields
Parameters = <>
SQL.Strings = (
'SELECT EmployeeID, LastName , FirstName ,Title '
'FROM Employees')
Left = 64
Top = 88
object ADOQuery1EmployeeID: TAutoIncField
FieldName = 'EmployeeID'
ReadOnly = True
end
object ADOQuery1LastName: TWideStringField
FieldName = 'LastName'
end
object ADOQuery1FirstName: TWideStringField
FieldName = 'FirstName'
Size = 10
end
object ADOQuery1Title: TWideStringField
FieldName = 'Title'
Size = 30
end
object ADOQuery1Calc1: TStringField
FieldKind = fkCalculated
FieldName = 'Calc1'
Calculated = True
end
object ADOQuery1Calc2: TFloatField
FieldKind = fkCalculated
FieldName = 'Calc2'
Calculated = True
end
end

Steve Zimmelman · Guest

If you follow the code, you'll see that clone only replaces the RecordSet
property. It does not duplicate the Ado component.

From the Help:
"Call Clone to make the recordset of the calling ADO dataset component a
duplicate of the recordset active in another TCustomADODataSet descendant
component."

"aaa.aaaa" <aaa.aaa (AT) aaa (DOT) net> wrote

aaa.aaaa · Guest

ok but if i try that

myClonedDataSet.FieldByName('MyOldCalutedField').AsValue

the systeme raise error "Field undetermined"

The Calculated fields are not cloned how can i clone them ?

Thanks

Steve Zimmelman wrote:

Steve Zimmelman · Guest

You can only clone the actual recordset that is derived from the database.
Calculated fields belong to the component, not the recordset.

You can't clone calculated fields, you must create them just as you did in
the original Ado component and assign them to an OnCalcFields event method.

You might be able to use something like this:

CloneFields(SrcAdoQuery,DestAdoQuery);

DestAdoQuery.Clone(SrcAdoQuery);

(*** Not Tested ***)

Uses DB ;

Procedure CloneFields(DataSet,DestDS:TDataSet);
Var
iMax : Integer ;
AFld : TField ;
Begin

if (DataSet = nil) or (DataSet.FieldCount = 0) or not DataSet.Active then
exit;

If DataSet.FieldCount > 0 then begin
iMax := DataSet.FieldCount ;
End Else Begin
DataSet.FieldDefs.Update;
iMax := DataSet.FieldDefs.Count ;
End;

For i := 0 to (iMax - 1) Do Begin
AFld := DestDS.FindField(DataSet.Fields[i].FieldName) ;
If (AFld <> Nil) Then AFld.Free ;
AFld :=
DefaultFieldClasses[DataSet.Fields[i].DataType].Create(DestDS);
AFld.Name := DestDS.Name +DataSet.Fields[i].FieldName;
AFld.FieldName := DataSet.Fields[i].FieldName;
AFld.FieldKind := DataSet.Fields[i].FieldKind ;
If (AFld is TStringField) Then Begin
TStringField(AFld).Size := DataSet.Fields[i].Size ;
End Else If (AFld is TBlobField) Then Begin
TBlobField(AFld).Size := DataSet.Fields[i].Size ;
End;
AFld.DataSet := DestDS;
End;
End;

You will still need to create an OnCalcFields event in the dataset that
receives the cloned RecordSet.

-Steve-

"aaa.aaaa" <aaa.aaa (AT) aaa (DOT) net> wrote

aaa.aaaa · Guest

Thanks a lot
I just modified one line

Steve Zimmelman · Guest

As long as the DataSet is closed you can free whatever fields you want.

"aaa.aaaa" <aaa.aaa (AT) aaa (DOT) net> wrote