How to force a Client DataSet to recalculate calculated and internal calculated fields?

delphi, delphi-xe2, tclientdataset

Solution

I achieve that with a helper (stripped here to the necessary), which allows to call the protected methods without any hack. Make sure to check for `DataSet.State = dsInternalCalc` inside OnCalcFields for fkInternalCalc fields.

type
  TClientDataSetHelper = class helper for TClientDataSet
  public
    function AssureEditing: Boolean;
    procedure InternalCalc;
  end;

function TClientDataSetHelper.AssureEditing: Boolean;
begin
  result := not (State in [dsEdit, dsInsert]);
  if result then
    Edit;
end;

procedure TClientDataSetHelper.InternalCalc;
var
  needsPost: Boolean;
  saveState: TDataSetState;
begin
  needsPost := AssureEditing;
  saveState := setTempState(dsInternalCalc);
  try
    RefreshInternalCalcFields(ActiveBuffer);
  finally
    RestoreState(saveState);
  end;
  if needsPost then
    Post;
end;

This can easily be expanded for normal calculated fields using `CalculateFields`. Although this shouldn't be necessary as calculated fields are recalculated whenever any other data field changes.

Problem

I have a `ClientDatSet` with a few `fkInternalCalc` fields. The CDS is not linked to any provider; instead it's filled on the fly. How can I force CDS to recalculate all the "calculable" fields? I can not call `Refresh()` because there is no provider to refresh data from. The only way I have come with so far has been to navigate through all records, which is not the best way. PS: I have read this question and this post, but I'm hoping for a more elegant way.

Original source

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