Calc. fields in TClientDataSet.

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6 total messages Started by Joaquin P. Wed, 11 Jan 2006 09:25

#65

Author: Joaquin P.
Date: Wed, 11 Jan 2006 09:25

15 lines
1582 bytes

Hi!

    I'm using a TClientDataSet component in a VCL.NET application, and I've 
defined several data and calculated fields.
    Everything is running ok, but I noticed about a 'rare behaviour' of 
calc. fields (TFloatField only):
    * Results of the calculation, having the decimal part '0' or '5' (i.e. 
'24' or '15,5' -we use comma as decimal separator, but I tried using decimal 
point with the same result-), are saved ALWAYS as '0' in the calc. field.
    * Results having any other decimal ('15,1', '15,23', '32,70', '32.70', 
...) are saved CORRECTLY.

    Please, can anybody help me?

    Thanks.

Re: Calc. fields in TClientDataSet.

#67

Author: Nick Hodges [TeamB]
Date: Wed, 11 Jan 2006 22:00

19 lines
1622 bytes

Joaquin P. wrote:

>  * Results of the calculation, having the decimal part '0' or '5'
> (i.e. '24' or '15,5' -we use comma as decimal separator, but I tried
> using decimal point with the same result-), are saved ALWAYS as '0'
> in the calc. field.    * Results having any other decimal ('15,1',
> '15,23', '32,70', '32.70', ...) are saved CORRECTLY.

Calculated fields aren't "saved" -- they only display the value that
you calculate for them.

Can you post a simple code example that illustrates the problem? It
sounds like perhaps you don't completely understand how floating point
math works in a 32-bit  processor....

-- 
Nick Hodges -- TeamB
Dunn Solutions Group -- http://www.dunnsolutions.com
Read my Blog -- http://www.lemanix.com/nickblog

Re: Calc. fields in TClientDataSet.

#68

Author: Joaquin P.
Date: Thu, 12 Jan 2006 09:25

63 lines
3508 bytes

   Perhaps I didn't explain myself sufficiently clear. I know that 
calculated fields are used for displaying values (not for save them); I just 
wanted to say 'assigned', instead of 'saved'.
   Anyways, I'll show a code example (it's as simple as enigmatic).:
...
type
  TVentas2Fr = class(TForm)
...
    tbMemDocLin: TClientDataSet;
    tbMemDocLinPvp: TFloatField;            {FieldKind: fkData}
    tbMemDocLinUdsVenta: TFloatField;    {FieldKind: fkData}
    tbMemDocLinCalPvp: TFloatField;        {FieldKind: fkCalculated}
...
procedure TVentas2Fr.tbMemDocLinCalcFields(DataSet: TDataSet);
begin
    // Assign to 'CalPvp' the result of multiplying 'Pvp' and 'UdsVenta':
    tbMemDocLinCalPvp.Value := tbMemDocLinPvp.Value * 
tbMemDocLinUdsVenta.Value;
end;
...

    I'm showing the value assigned to 'CalPvp' in a TDBText component, 
called 'DBText1', on my form. Let's suppose some different cases:

a) tbMemDocLinPvp.Value := 4;  tbMemDocLinUdsVenta.Value := 8;
    In this case, DBText1 shows 0, instead of 32 .
b) tbMemDocLinPvp.Value := 4.1;  tbMemDocLinUdsVenta.Value := 8;
    DBText1 shows 32.8 (correct!).
c) tbMemDocLinPvp.Value := 5.5;  tbMemDocLinUdsVenta.Value := 3;
    DBText1 shows 0, instead of 16.5 .
d) tbMemDocLinPvp.Value := 5.6;  tbMemDocLinUdsVenta.Value := 3;
    DBText1 shows 16.8 (correct!).

     I hope that these lines can help to understand the nature of the 
problem, and to obtain a satisfactory solution.

    Thanks.

//
//
//

"Nick Hodges [TeamB]" <nickhodges@gmail.com> escribi� en el mensaje 
news:43c58e16$1@newsgroups.borland.com...
> Joaquin P. wrote:
>
>>  * Results of the calculation, having the decimal part '0' or '5'
>> (i.e. '24' or '15,5' -we use comma as decimal separator, but I tried
>> using decimal point with the same result-), are saved ALWAYS as '0'
>> in the calc. field.    * Results having any other decimal ('15,1',
>> '15,23', '32,70', '32.70', ...) are saved CORRECTLY.
>
> Calculated fields aren't "saved" -- they only display the value that
> you calculate for them.
>
> Can you post a simple code example that illustrates the problem? It
> sounds like perhaps you don't completely understand how floating point
> math works in a 32-bit  processor....
>
> -- 
> Nick Hodges -- TeamB
> Dunn Solutions Group -- http://www.dunnsolutions.com
> Read my Blog -- http://www.lemanix.com/nickblog

Re: Calc. fields in TClientDataSet.

#69

Author: Joaquin P.
Date: Thu, 12 Jan 2006 09:31

23 lines
1854 bytes

Just remember I'm working in a Delphi-VCL.NET project with BDS2005 and 
Updates 1,2 & 3 installed.


"Joaquin P." <jpaton@proib.com> escribi� en el mensaje 
news:43c4ce3e@newsgroups.borland.com...
> Hi!
>
>    I'm using a TClientDataSet component in a VCL.NET application, and I've 
> defined several data and calculated fields.
>    Everything is running ok, but I noticed about a 'rare behaviour' of 
> calc. fields (TFloatField only):
>    * Results of the calculation, having the decimal part '0' or '5' (i.e. 
> '24' or '15,5' -we use comma as decimal separator, but I tried using 
> decimal point with the same result-), are saved ALWAYS as '0' in the calc. 
> field.
>    * Results having any other decimal ('15,1', '15,23', '32,70', '32.70', 
> ...) are saved CORRECTLY.
>
>    Please, can anybody help me?
>
>    Thanks.
>

Re: Calc. fields in TClientDataSet.

#70

Author: Joaquin P.
Date: Thu, 12 Jan 2006 13:39

2 lines
1194 bytes

I've posted a full-code example at borland.public.attachments (Subject: 
Calc. fields in TClientDataSet: Full example).

EUREKA!!!

#71

Author: Joaquin P.
Date: Thu, 12 Jan 2006 15:37

4 lines
1097 bytes

The solution: replace the value of the 'FieldKind' property, 'fkCalculated', 
by 'fkInternalCalc'.

Thanks, Ivan.

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