Using TMemDataset
lazarus / 16-Databases

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rdxdt · 2025-06-24 13:25

Hi i created the field defs on my TMemDataSet, Assuming it serves a
purpose like TClientDataSet from VCL or TFDMemTable from FireDAC, now
when i try to append a record to it, it gives me field not found.
on TClientDataSet i would call CreateDataSet and then it would work
normally, how can i proper use the TMemDataSet to have a dataset in
memory with the field defs that i defined?
Thanks

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egsuh · 2025-06-26 06:40

TBufDataSet is recommended instead of TMemDataSet.

TBufDataSet.CreateDataSet will create dataset.

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Thaddy · 2025-06-26 07:13

Correct. TMemdataset has many flaws / limitations that  you need to be
aware of.
Use TBufDataset instead.

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rdxdt · 2025-06-26 10:15

Thanks for all the replies folks, i will use the TBufDataset then.

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LacaK · 2025-06-30 09:30

To respond to original question:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   MemDs :=
TMemDataset.Create(nil);  MemDS.FieldDefs.Add('ID',ftInteger); 
MemDS.FieldDefs.Add('NAME',ftString,50);  MemDS.CreateTable; 
MemDS.Open;

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Richard Marriott · 2025-07-03 23:54

There is a good tutorial on this website on how to get all the
TDataset descendants (including TMemDataset) up and running. Look at
TUTORIALS on the main menu.

TDataset7.Wordpress.com

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Thaddy · 2025-07-04 15:08

There are better tutorials on OUR wiki, including a warning that
TMemdataset has severe limitations and you should consider TBufDataset
for real-world applications. And looks to me more like you expect.

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Richard Marriott · 2025-07-05 23:42

I wasn't suggesting that the OP should not try the Wiki first, but the
Wiki doesn't always show the answer to the exact question needing to
be answered. There are many other sources on the Web that can give
insights into Lazarus programming. I suggested the above website
because it DOES answer the specific question in a way that is easy for
newbies to understand. In many cases the Wiki is written by
experienced Lazarus programmers and aimed at other experienced
programmers, and it takes a newbie (like me) a fair amount of time to
get his/her head around the answer, The more alternative sources the
more angles that can be seen to a problem.

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Thaddy · 2025-07-06 06:44

The wiki is written by - mostly but not always - experienced
programmers with the intention to document features of the language in
such a way that it is also understandable for beginners.
It is also a source of documentation but not official documentation.
(Beginners should not choose TMemDataSet is one such advice)

E.g. this entry is quite comprehensive if you still want to use it:
https://wiki.freepascal.org/How_to_write_in-
memory_database_applications_in_Lazarus/FPC