How can I access to FUpdateBuffer of TBufDataset?
lazarus / 16-Databases

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taqtaq · 2012-12-15 14:41

How can I access to FUpdateBuffer of TBufDataset?

I want to modify the  Applyupdates method from TBufDataset and I need
to access to FUpdateBuffer to manage  records that i want to save into
the db and wich not, but i can't.

I hope to explain

I have  a function to copy a record to a tbufdataset. I use it to copy
only records allocated into a bufdataset or Tsqlquery, because if i
use loadfromstream, it moves all data from the database and i don't
want that, i need only a packetrecord saved.

The function is very simple and needs work:

Code: [Select]
procedure CopioRegistro(Datasetorigen, Datasetdestino: TBufDataSet);
var
  ar: Integer;
begin
  if (Datasetorigen <> nil) and (Datasetdestino <> nil) then
  begin
    Datasetdestino.Append;
     for ar := 0 to Datasetorigen.FieldCount - 1 do
    begin
      if
(Datasetdestino.Fields.FindField(Datasetorigen.Fields[ar].FieldName)
<> nil) then
       
Datasetdestino.FieldByName(Datasetorigen.Fields[ar].FieldName).Value
:= Datasetorigen.FieldByName
          (Datasetorigen.Fields[ar].FieldName).Value;
    end;
    Datasetdestino.post;
  end;
end;

procedure CopioTabla(Tablaorigen, Tabladestino: TBufDataSet);
begin
  if (Tablaorigen = nil) or (Tabladestino = nil) then  Exit;
  Tablaorigen.Active := True;
  Tabladestino.Active := True;

  Tablaorigen.First;
  for ar := 1 to tablaorigen.RecordCount do
  begin
    CopioRegistro(tablaorigen, tabladestino);
    Tablaorigen.Next;
  end;

end;



After copying all, i want to modify some records for apply to
database, but after to use the funcion "CopioTabla" the records are
marked as inserted in FUpDateBuffer of TBufDataset and I don't want it
because then, when move all to SQLQuery to use applyupdates, the
sqlquery considers the records should be inserted but not updated.

The mechanism is:
1 : Open SQLQuery from Database.
2 : Save packetrecords into TBufDataset with "CopioTabla". (only few
records)
3 : Close SQLQuery. (Close transaction too)
4 : Readfromstream from TBufDataset into SQLQuery.
5 : Work with new datapacket. (modify, delete, insert records)
6 : Open Transaction
7 : Applyupdates (PROBLEM: all the records are consideres like
inserted)


Well, I hope you can understand me
Thanks

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Foxy · 2012-12-15 22:57

Hi taqtaq

Short answer is you cannot access it as it is a 'private' member in
the TCustomBufDataset object
(without exposing it through  'protected' Get/Set routines - That
route could be dangerous)

You might try something like the following :-

Scan your BufDataset exposing the the TDataSet BookMarks. For every
record whose BookMark.Flag = bfInserted
change that BookMark.Flag := bfCurrent and add the record to your own
create stream.  When you have scanned
the whole BufDataSet then use SaveToStream to point your stream at the
SQLQuery.

No idea if it works but better than exposing a private dynamic array.

Good Luck
Martin Fox