• Create the variable (allocate storage) in the component constructor
• Deallocate the variable in the destructor
• Use
  xx := Assign(Value) ;
  instead of just the assignment operator
  xx := Value ;

If these rules are not followed, then Delphi will crash (completely close) and you will loose any unsaved work.

These code fragments are from a working component

  TmcTearoff_Windows = class(TComponent)
  private
    FIcon         : TIcon;
    procedure SetIcon(Value: TIcon);
  public
    constructor Create(AOwner: TComponent); override;
    destructor  Destroy;                    override;
  published
    property Icon : TIcon  read FIcon write SetIcon;
  end;

constructor TmcTearoff_Windows.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FIcon        := TIcon.Create;
  FIcon.Width  := GetSystemMetrics(SM_CXSMICON);
  FIcon.Height := GetSystemMetrics(SM_CYSMICON);
end;

destructor TmcTearoff_Windows.Destroy;
begin
  FIcon.Free;
  inherited;
end;

procedure TmcTearoff_Windows.SetIcon(Value: TIcon);
begin
  FIcon.Assign(Value);
end;

URL: http:// cpcug.org / user / clemenzi / technical / Languages / Delphi / ComponentProperties_Icons.html