Cache current DataSet and restore inside loop

[BKeffer]

Hey guys!

I'm currently thinking about to buy this nice component. But first I want to make sure If it is the right tool.

So, my question is the following:
How is it possible to save the current MyTable-state while you loop through the dataset. What I mean is

Code: Select all

  FAutomat.OrderFields:= 'recno ASC';
  FAutomat.Open;
  while not FAutomat.Eof do
  begin
    FAutomat.PushState; // thats what I'm looking for -> should save the state

    // Do a different select
    FAutomat.AddWhere('name="Test"');   
    FAutomat.Open;

    FAutomat.PopState; // should restore the pushed state
  end;

As you can see, the state of the dataset should be the same like before pushsate and after popstate.

Can you guys help me? Would be very nice!

Best regards
Benjamin

[BKeffer]

I was thinking about somthing like this:

Code: Select all

procedure TMyTable.PushState;
var Batch: TCRBatchMove;
begin
  FPushedDataSet:= TVirtualTable.Create(nil);
  Batch:= TCRBatchMove.Create(nil);
  Batch.Source:= Self;
  Batch.Destination:= FPushedDataSet;
  Batch.Execute;

  FPos:= Self.CurrentRecord;
  FConditions:= Self.Conditions;
  FOrder:= Self.OrderFields;
end;

procedure TMyTable.PopState;
begin
  Self.Conditions:= FConditions;
  Self.OrderFields:= FOrder;
  Self.SetCurrentRecord(FPos);

  Self.Data:= FPushedDataSet.GetData;
end;

However, this doesn't work :-/ Any help?

[ViktorV]

To solve your task, you better use a separate dataset for executing additional queries.

[BKeffer]

Thanks for your reply!

And in general, how can I copy one DataSet to another (only in memory)?

[ViktorV]

To solve your task, you can assign a TMyQuery (TMyTable) to a TVirtualTable. You can read about to fill TVirtualTable with data from another TDataSet component in the VirtualTable help: https://www.devart.com/virtualdac/docs/ ... bject).htm

[BKeffer]

Thank you!

[ViktorV]

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