Design Problem (Shapes)

[Sir Rufo]

Wenn du das flexibel erweitern möchtest, dann nimm eine Shape-Klasse und eine ShapeStrategy-Klasse.
Hier mal skizziert, wie das geht:

Delphi-Quellcode:

type
  TShapeStrategy = class abstract
  protected
    procedure Paint( ACanvas : TCanvas ); virtual; abstract;
  end;

  TShapeStrategyClass = class of TShapeStrategy;

  TShape = class( TGraphicControl )
  private
    FStrategyName : string;
    FStrategy : TShapeStrategy;
    procedure SetStrategyName( const Value : string );
  protected
    procedure Paint; override;
  public
    class procedure RegisterStrategy( const AName : string; AStrategy : TShapeStrategyClass );
  published
    property StrategyName : string read FStrategyName write SetStrategyName;
  end;

procedure TShape.Paint;
begin
  if Assigned( FStrategy ) then
    FStrategy.Paint( Canvas );
end;