CalcFields events

rbuser

Var
balance: Real;

procedure TForm1.Query1CalcFields(DataSet: TDataSet);
Var
amount:real;
begin
amount:=Query1.FieldByName('AMOUNT').AsFloat;
if Query1amount.Value>0 then begin
Query1debit.Value:=amount;
balance:=balance+amount;
end
else begin
Query1credit.Value:=abs(amount);
balance:=balance-abs(amount);
end;
Query1balance.Value:=balance;

end;

the debit, credit and balance is calculated field, when I try this coding
and display with the DBGrid, I can get the correct amount for the balance
field, but when I try to display it in report builder, I was unable to get
the correct balance. it look like because this events was fired many times
in report builder, because when i switch to page 2 and switch back to page
1, the value for the balance will be increase. so is any way to limit the
code only fired once which can let me to get the correct balance?

nardmoseley

OnCalcFields will fire each time the record position changes in the dataset.
You should only use this event to perform a calculation that depends on data
field values in the same record. Never use this event to perform
calculations across records. If you build an examples that scrolls back and
forth thru the dataset, you will see that the calculations break.
ReportBuilder does not simply traverse the dataset from front to back. Check
out the Calculations tutorial in the Developers Guide and the Calculations
thread of the Tech Tips newsgroups for details on performing calculations.


--
Nard Moseley
Digital Metaphors Corporation
http://www.digital-metaphors.com

rbuser

Thanks!
I was try to use ppVariable1.OnCalc to calculate the balance, the result
look like ok, but the problem for me is sometime end user may accidently
delete the ppVariable during designer mode (designer.show), so is any way
for me to lock the ppVariable which let the end user unable to delete? and
if I want to using ppVariable to calculate balance, than end user may unable
to select the balance for the data field like other DBtext, because it was
fix with ppVariable.

Rgds
CH

nardmoseley

Try using a summary dataset. Either use SQL to create a summary query that
contains the calculated results or perhaps pre-process the data to build a
temp table that contains the summarized calcs. Then use DBText inside the
report.

--

Nard Moseley
Digital Metaphors Corporation
www.digital-metaphors.com