如果还有日期时间字段，Delphi 10.4 无法在 DBGrids 上显示十进制 (5,2) BCD 字段

Question

When I have a ClientDataset with datetime fields and decimal(5,2) fields, Delphi 10.4 can't show them on a TDBGrid, it raises a convert exception.

I have prepared an small test project to show this error (my real data comes from SQL Server, although I can get the same error filling the Clientdataset manually).

procedure TForm1.FormCreate(Sender: TObject);
var ClientDataset: TClientDataset;
    Datasource: TDatasource;
    DBGrid: TDBGrid;
begin
  ClientDataset := TClientDataset.Create(Self);
  ClientDataset.FieldDefs.Add('Id', ftInteger);
  ClientDataset.FieldDefs.Add('Date', ftDateTime);
  ClientDataset.FieldDefs.Add('Decimal', ftBCD, 2);
  ClientDataset.FieldDefs.Find('Decimal').Precision := 5;
  ClientDataset.CreateDataSet;
  Datasource := TDatasource.Create(Self);
  Datasource.Dataset := ClientDataset;

  ClientDataset.Insert;
  ClientDataset.FieldValues['id'] := 1;
  ClientDataset.FieldValues['Date'] := Now;
  ClientDataset.FieldValues['Decimal'] := 7.55;
  ClientDataset.Post;
  ClientDataset.Insert;
  ClientDataset.FieldValues['id'] := 2;
  ClientDataset.FieldValues['Date'] := Now;
  ClientDataset.FieldValues['Decimal'] := 8.2;
  ClientDataset.Post;

  DBGrid := TDBGrid.Create(Self);
  DBGrid.Parent := Self;
  DBGrid.Align := alClient;
  DBGrid.Datasource := Datasource;
end;

It raises this exception: '8200@' is not a valid integer value

A decimal(18,2) doesn't have this problem, if I comment the line ClientDataset.FieldDefs.Find('Decimal').Precision:= 5;then no error is raised.

Also, if there is no datetime field then no error is raised either. This runs fine:

procedure TForm1.FormCreate(Sender: TObject);
var ClientDataset: TClientDataset;
    Datasource: TDatasource;
    DBGrid: TDBGrid;
begin
  ClientDataset := TClientDataset.Create(Self);
  ClientDataset.FieldDefs.Add('Id', ftInteger);
  ClientDataset.FieldDefs.Add('Decimal', ftBCD, 2);
  ClientDataset.FieldDefs.Find('Decimal').Precision := 5;
  ClientDataset.CreateDataSet;
  Datasource := TDatasource.Create(Self);
  Datasource.Dataset := ClientDataset;

  ClientDataset.Insert;
  ClientDataset.FieldValues['id'] := 1;
  ClientDataset.FieldValues['Decimal'] := 7.55;
  ClientDataset.Post;
  ClientDataset.Insert;
  ClientDataset.FieldValues['id'] := 2;
  ClientDataset.FieldValues['Decimal'] := 8.2;
  ClientDataset.Post;

  DBGrid := TDBGrid.Create(Self);
  DBGrid.Parent := Self;
  DBGrid.Align := alClient;
  DBGrid.Datasource := Datasource;
end;

Do you think that this could be fixed without having to replace all my decimal(5,2) fields with decimal(18,2) fields?.

UPDATE: This is a problem specific of the ClientDataset. If I open the same data on a TADOQuery or TFDMemTable (with the exact same datetime and decimal(5,2) BCD fields), Delphi 10.4 shows the DBGrid without any issue.

The problem is also specific of the DBGrid. There is no problem displaying those fields on DBEdits.

Answer 1

Changes have been made in version 10.4 on the unit Data.FmtBcd about functions BCDToCurr e BCDToCurrency.

Delphi 10.3

function BCDToCurr(const BCD: TBcd; var Curr: Currency): Boolean;
  Curr := StrToCurr(string(Bcd));
  Result := True;
end;

function BCDToCurrency(const BCD: TBcd): Currency;
begin
  Result := StrToCurr(string(Bcd)); 
end;

Delphi 10.4

function BCDToCurr(const BCD: TBcd; var Curr: Currency): Boolean;
var
  B: TBcd;
  S: string;
const
  DecimalSeparator = '.';
begin
  // B := BCD * 10000;
  B := BCD;
  if BcdScale(B) >= 4 then
    Dec(B.SignSpecialPlaces, 4)
  else if BcdPrecision(B) <= (MaxFMTBcdFractionSize - 4) then
    Inc(B.Precision, 4)
  else
    OverflowError(SBcdOverflow);

  S := BcdToStr(B, DecimalSeparator);
  Round(S, DecimalSeparator, 0);
  // The real format of Currency type is Int64.
  PInt64(@Curr)^ := StrToInt64(S);
  Result := True;
end;

function BCDToCurrency(const BCD: TBcd): Currency;
begin
  BCDToCurr(BCD, Result);
end;

So, with precision:=5 in BCDToCurr function:

else if BcdPrecision(B) <= (MaxFMTBcdFractionSize - 4) then Inc(B.Precision, 4)

and B.Precision increment to 9. The variable Curr then takes an incorrect value.

Answer 2

I reported the bug and now has been fixed in the recent Delphi 10.4 Update 1.