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2007-01-10 11:01:20 PM
delphi144
Hi,
Does anyone know how to force an OnCalcFields event to get launched? I
need this ability because I have got a calculated field that depends on
data not in the TDataSet (in a TStringList), so I need to recalculate
its value if ever the contents of the TStringList changes.
I usually just call Edit / Cancel, but since the dataset I am working
with right now is read-only, I was wondering if there's another
solution.
Any ideas?
BTW, I am using the BDE in this application.
--
Best regards,
Jonathan Neve
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Jonathan Neve[Microtec] writes:
if (pDataSet->OnCalcFields != NULL)
{
pDataSet->OnCalcFields(this);
}
Best Regards,
Shane
 

"Jonathan Neve[Microtec]" <XXXX@XXXXX.COM>writes news:XXXX@XXXXX.COM...
Andrew
 

Hello Jonathan
Actually, there are no legal ways to recalculate only fields.
I think, Edit & Cancel will be most cheap one.
Regards,
Dmitry
--
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Hello,
OnCalcFields is called as part of loading records into the TDataset's
cache (all records currently visible on screen are stored in a cache).
Refreshing the cache will therefore recalculate all data. Calling
TDataset.Resync([]) will just do that.
I can not remember whether TDataset.Refresh will do the same thing but I
expect that Refresh only frees the cached field values and not the
caclulated data. So if Refresh doesn't work, you will should call Resync().
Calling Edit/Cancel actually does the same thing.
Regards,
Kees
Jonathan Neve[Microtec] writes:

Hi Shane,
Shane Stump writes:
DataSet is in a specific mode. If I call it at an arbitrary time of my
own choosing, that is no different than simply setting a value to the
calculated field directly, which, unless I am much mistaken, doesn't
work.
--
Best regards,
Jonathan Neve
_______________
CopyTiger - advanced database replicator for Interbase/Firebird!
Web : www.microtec.fr/copycat/ct
_______________________________________
CopyCat - database replication components for Delphi/C++Builder!
Web : www.microtec.fr/copycat/cc
 

Andrew writes:
end, I solved my problem by simply calling :
RefreshQuery(qry);
RefreshQuery is an RX (IIRC) procedure that simply closes the query,
reopens it, and repositions the cursor where it was. This works fine,
but it is overkill. I seem to remember that Refresh isn't implemented in
TQuery (which is what I am using here, TRxQuery to be more precise).
--
Best regards,
Jonathan Neve
_______________
CopyTiger - advanced database replicator for Interbase/Firebird!
Web : www.microtec.fr/copycat/ct
_______________________________________
CopyCat - database replication components for Delphi/C++Builder!
Web : www.microtec.fr/copycat/cc
 

Dmitry Arefiev writes:
something. It would be nice to have an extremely simple method added to
TDataSet, something like "RefreshCalcFields". it is probably not common
to need this, but I must not be the only one.
I agree, Edit & cancel is a good trick, except that it doesn't work
when the dataset is read-only.
--
Best regards,
Jonathan Neve
_______________
CopyTiger - advanced database replicator for Interbase/Firebird!
Web : www.microtec.fr/copycat/ct
_______________________________________
CopyCat - database replication components for Delphi/C++Builder!
Web : www.microtec.fr/copycat/cc
 

Kees Vermeulen writes:
that once before, but I am not sure. Anyway, for now I am simply
refreshing the query, which works fine.
--
Best regards,
Jonathan Neve
_______________
CopyTiger - advanced database replicator for Interbase/Firebird!
Web : www.microtec.fr/copycat/ct
_______________________________________
CopyCat - database replication components for Delphi/C++Builder!
Web : www.microtec.fr/copycat/cc
 

Jonathan Neve[Microtec] writes:
type
TTableUnprotected = class(TTable);
procedure RecalcCurrentRecord(Tabe: TTable);
begin
with TTableUnprotected(Table) do begin
GetCalcFields(ActiveBuffer);
DataEvent(deRecordChange, 0); // this force linked controls to
refresh their data
end;
end;
eLion
 

Jonathan Neve[Microtec] writes:
call a TkbmMemTable's OnCalcFields manually but I know what the state of
the dataset is in.
Best Regards,
Shane
 

This is what I use on TkbmMemTables when I need to force an OnCalc.
Give if a try and see if it works for you.
type
TDataSetHack = class(TDataSet);
Procedure ForceOnCalcFieldsEvent(ADataSet : TDataSet);
begin
If Not (ADataSet.State in ([dsCalcFields, dsInternalCalc, dsInActive]))
then
TDataSetHack(ADataSet).GetCalcFields(TDataSetHack(ADataSet).CalcBuffer);
end;
Stuart
--