2

The following Delphi function can be used to add a fkInternalCalc to a TClientDataset. This is useful because I can store some information for each record, make calculation or store temporary flag.

The same code does not work in Lazarus, it stops on DataSet.FieldDefs.Update.

Are there means to achieve the same functionality? Remember that one could change database fields and apply the changes made.

A working Delphi code using the function is:

AddDummyField(qry,TIntegerField,'PROCESS_ACTION');
qry.Open;
...

function AddDummyField(Dataset:TDataset;fieldClass:TFieldClass;fieldName:string;size:integer):TField;
var
  i: Integer;
begin

  if Dataset.FieldDefs.Count = 0 then
  begin
    DataSet.FieldDefs.Update;

    for i := 0 to DataSet.FieldDefs.Count - 1 do
      DataSet.FieldDefs[i].CreateField(DataSet);
  end;

  Result := Dataset.FindField(fieldName);

  if Result <> nil then
    exit;

  Result := fieldClass.Create(Dataset);
  Result.FieldName := fieldName;
  Result.FieldKind := fkInternalCalc;
  Result.DataSet := Dataset;

  if size>0 then
    Result.Size := size;
end;
Jako
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1 Answers1

0

You have to open the dataset before.

...
DataSet.Open;
DataSet.FieldDefs.Update;
DataSet.Close;

for i := 0 to DataSet.FieldDefs.Count - 1 do
  DataSet.FieldDefs[i].CreateField(DataSet);
...
max68
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