[Lazarus] object type: strange behaviour

[Graeme Geldenhuys]

Op 2010-10-22 21:55, Hans-Peter Diettrich het geskryf:
> 
> Delphi Objects should only be used with TP7 member types.
...snip...
> Note that Object types with no ancestors 
>   are properly initialized and finalized...

Thanks, I didn't know about the bug you mention. Luckily for me, when I
need a hierarchy I always use Classes, but for a single type that will
never have descendants, I often use Objects with member methods.

Here are two examples of Object usage in fpGUI:

type
  TfpgRect = object  // not class for static allocations
    Top: TfpgCoord;       // TfpgCoord is an alias for Integer
    Left: TfpgCoord;
    Width: TfpgCoord;
    Height: TfpgCoord;
    procedure SetRect(aleft, atop, awidth, aheight: TfpgCoord);
    function  Bottom: TfpgCoord;
    function  Right: TfpgCoord;
    procedure SetBottom(Value: TfpgCoord);
    procedure SetRight(Value: TfpgCoord);
  end;


  TfpgPoint = object  // not class for static allocations
    X: integer;
    Y: integer;
    procedure SetPoint(AX, AY: integer);
    function  ManhattanLength: integer;
    function  ManhattanLength(const PointB: TfpgPoint): integer;
  end;


And because an instance can be allocated without a constructor, and
automatically free'ed, Object is really useful.



Regards,
  - Graeme -

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