Params.asBlob assignment under FireDAC gives W1058

Question

The FireDAC sample project (demonstrating ArrayDML) c:\Users\Public\Documents\Embarcadero\Studio\19.0\Samples\Object Pascal\Database\FireDAC\Samples\Comp Layer\TFDQuery\ExecSQL\Batch\Batch.dproj compiles with two // W1058 Implicit string cast with potential data loss from string to rawbytestring warnings on the Params[2].AsBlobs assignments indicated with //W 1058:

procedure TfrmBatch.btnExecSQLClick(Sender: TObject);
var
  i: Integer;
  iTm: LongWord;
begin
  qrySelect.Open;
  qrySelect.ServerDeleteAll(True);
  qrySelect.Close;
  with qryBatch do
    if cbxBatchExec.Checked then begin
      Params.ArraySize := StrToInt(edtArraySize.Text);
      iTm := GetTickCount;
      for i := 0 to Params.ArraySize - 1 do begin
        Params[0].AsIntegers[i] := i;
        Params[1].AsStrings[i] := 'string' + IntToStr(i);
        Params[1].Size := 20;
        if cbxInsertBlob.Checked then
          Params[2].AsBlobs[i] := 'blob' + IntToStr(i);    // W1058 
      end;
      Execute(Params.ArraySize);
      iTm := GetTickCount - iTm;
    end
    else begin
      Params.ArraySize := 1;
      iTm := GetTickCount;
      for i := 0 to StrToInt(edtArraySize.Text) - 1 do begin
        Params[0].AsInteger := i;
        Params[1].AsString := 'string' + IntToStr(i);
        Params[1].Size := 20;
        if cbxInsertBlob.Checked then
          Params[2].AsBlob := 'blob' + IntToStr(i);       // W1058 
        ExecSQL;
      end;
      iTm := GetTickCount - iTm;
    end;
  StatusBar1.SimpleText := 'Time executing is ' + FloatToStr(iTm / 1000.0) + ' sec.';
  qrySelect.Open;
end;

What is the correct way to solve this? (Under FireDAC the AsBlobs has changed to TFDByteString = RawByteString under Windows). Both a cast as RawByteString() or a Params[2].Value assignment make the compiler warning go away but I'm unsure it this won't lead to potential problems...

Answer 1

If you decide storing binary BLOB data in a String type variable, you can lose them, and by adding typecast to RawByteString before that parameter value assignment you just say the compiler, that you agree with a potential data loss. There's nothing more than that.

Correct way is storing your BLOB data in RawByteString type variable for such parameter.