Property's "stored" bug...

[Renate Schaaf]

Geht es hier um float-properties? Der bug ist bekannt seit Delphi 1, wurde angemahnt, und kam zurück mit "as designed". Ray Lischner hat eine Lösung gefunden, ich poste hier mal den Teil einer Komponente für Delphi 1, der die Lösung beinhaltet und erklärt. Falls das nicht das Problem ist, nevermind.

Delphi-Quellcode:

...
  protected
  procedure ReadD2WorldXw(Reader: TReader);
  procedure WriteD2WorldXW(Writer: TWriter);
  procedure DefineProperties(Filer: TFiler); override;  
 
  published
  property D2WorldXW: extended read xwd2 write setxwd2 stored false;
  {Don't worry about the stored false in all of these. They get stored:
    see override of DefineProperties. The default storing process never
    writes a value 0 of a float property to the dfm-file and the default
    value set in the constructor is used instead. So if that default is
    <>0, a value 0 can never be set. Overriding DefineProperties fixes it
     (workaround by Ray Lischner).
    Stored false is used, so the property is not stored twice. (Thanks to
    Joe Herb for the tip)}

...

procedure TMathImage.ReadD2WorldXW(Reader: TReader);
begin
  xwd2 := Reader.ReadFloat;
end;

procedure TMathImage.WriteD2WorldXW(Writer:TWriter);
begin
  Writer.WriteFloat(xwd2);
end;

procedure TMathImage.DefineProperties(Filer: TFiler);
begin
  inherited DefineProperties(Filer);
  with Filer do
  begin
    DefineProperty('D2WorldXW', ReadD2WorldXW, WriteD2WorldXW, true);
  end;
end;