TmemTable has not onCalcFields event?
lazarus / 16-Databases

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dpap · 2025-02-02 20:19

I want to use a TMemTable for temporary record storing but, as I saw,
doesn't exist a onCalcFields. Is there a similar memTable (or can I
add) this event?

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Zvoni · 2025-02-03 07:49

Quote from: dpap on February 02, 2025, 09:19:30 pmI want to use a
TMemTable for temporary record storing but, as I saw, doesn't exist a
onCalcFields. Is there a similar memTable (or can I add) this event?

There is no TMemTable.
Do you mean TMemDataset?

And why would you expect an OnCalcFields-Event?
https://wiki.freepascal.org/TMemDataset (Yes, i know: Wiki is not
Documentation, but i was too lazy to search further)

QuoteA TMemDataset descendant acts like a cursor on a table or query-
result.There are no calculated fields in a QUERY-RESULT

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dpap · 2025-02-03 09:17

Yes, I mean TmemDataset. I want to have some fields in the table that
act as lookup fields, and due to TmemDataset's lack of ability to have
lookup fields, I plan to calculate them in the onCalcFields event
using the locate method.
Yes, I know I can write a function that calculates these values ​​when
needed, but I would prefer the onCalcFields event.

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wp · 2025-02-03 09:44

Maybe you should try TBufDataset. It is a memory table, too, but is
more complete.

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dpap · 2025-02-04 07:38

I know this but TBufDataset needs a file to write/read and this is not
convenient for me

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Thaddy · 2025-02-04 08:33

Quote from: dpap on February 04, 2025, 08:38:50 amI know this but
TBufDataset needs a file to write/read and this is not convenient for
me
To my knowledge that is not true.
Just call Buffdataset.CreateDataset; // I tested that just now!!
It does not need a filename.
And the use of Tmemtable is discouraged anyway.
The code should be marked as deprecated.

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egsuh · 2025-02-09 07:46

TMemDataSet does not, but TBufDataSet has OnCalcFields event handler.
So, you should use TBufDataSet. You do not need a file for it.

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Richard Marriott · 2025-07-05 23:57

Try this note on how to set up calculated fields using OnCalcFileds:
https://tdataset7.wordpress.com/how-to-use-tmemdataset-in-code-and-ide