ObjectDataSet - allow sorting by any object

[VlaPr]

The code currently do not support sorting by any object. The procedure CompareRecords is virtual, but uses private variables that disallow to implement own sorting (that's why I have classified this as a bug).

It can be solved for example adding an onCompareRecord event where user can implement his own rules ...

function TObjectDataSet.CompareRecords(const left, right: TObject): Integer;
var
  i: Integer;
  fieldInfo: TIndexFieldInfo;
  leftValue, rightValue: TValue;
begin
  Result := 0;

  for i := 0 to High(fIndexFields) do
  begin
    fieldInfo := fIndexFields[i];
    leftValue := fieldInfo.Prop.GetValue(left);
    rightValue := fieldInfo.Prop.GetValue(right);

    // Added new Event onCompareRecord
    if Assigned(fonCompareRecord) then
    begin
      Result := fonCompareRecord(leftValue, rightValue);
      if fieldInfo.Descending then
        Result := -Result;
      if Result <> 0 then
        Exit;
    end;
    //

    Result := leftValue.CompareTo(rightValue);
    if fieldInfo.Descending then
      Result := -Result;

    if Result <> 0 then
      Exit;
  end;
end;

[Stefan Glienke]

Sorting on the TObjectDataSet itself is still subject to change (or even removed as most UI controls like grids have their own sorting functionality).