TNotifyEvent Objektbezogen in Variable speichern

[KrasserChecker]

Scheinbar scheint ein Event "in Delphi" doch irgendwie anders gehandhabt zu werden, als ausschließlich über einen Zeiger.

Bzgl. einer Alternative würde ich daher vorschlagen einfach das Event über einen Wrapper zu kapseln:

Delphi-Quellcode:

type
  THAL_ObserverItem = class(TObject)
  private
    FEvent: TNotifyEvent;
  public
    constructor Create(iEvent: TNotifyEvent);
  public
    property Event: TNotifyEvent read FEvent write FEvent;
  end;

  THAL_Observer = class(TComponent)
  private
    FListSubscriber: TObjectList;
  protected
    function IndexOfEvent(_Event: TNotifyEvent): Integer;
  public
    procedure NotifySubscriber(_Sender: TObject);

    procedure RegisterSubscriber(_Event: TNotifyEvent);
    procedure UnRegisterSubscriber(_Event: TNotifyEvent);

    constructor Create(_Sender: TComponent); override;
    destructor Destroy; override;
  end;

[...]

{ THAL_ObserverItem }

constructor THAL_ObserverItem.Create(iEvent: TNotifyEvent);
begin
  inherited Create;
  FEvent := iEvent;
end;

{==============================================================================}

{$Region 'constructor THAL_Observer.Create(_Sender: TComponent);'}
constructor THAL_Observer.Create(_Sender: TComponent);
begin
  try
    inherited Create(_Sender);

    FListSubscriber := TObjectList.Create;
  except
    on E: Exception do begin
    end;
  end;
end;
{$EndRegion}

{==============================================================================}

{$Region 'destructor THAL_Observer.Destroy;'}
destructor THAL_Observer.Destroy;
begin
  try
    FreeAndNil(FListSubscriber);

    inherited Destroy;
  except
    on E: Exception do begin
    end;
  end;
end;

function THAL_Observer.IndexOfEvent(_Event: TNotifyEvent): Integer;
var i: Integer;
begin
  for i := 0 to FListSubscriber.Count - 1 do
    if @THAL_ObserverItem(FListSubscriber[i]).Event = @_Event then
    begin
      Result := i;
      Exit;
    end;
  Result := -1;
end;

{$EndRegion}

{==============================================================================}

{$Region 'procedure THAL_Observer.NotifySubscriber(_Sender: TObject);'}
procedure THAL_Observer.NotifySubscriber(_Sender: TObject);
var
  i: integer;
begin
  try
    for i := 0 to FListSubscriber.Count - 1 do begin
      THAL_ObserverItem(FListSubscriber[i]).Event(Self);
    end;
  except
    on E: Exception do begin
    end;
  end;
end;
{$EndRegion}

{==============================================================================}

{$Region 'procedure THAL_Observer.RegisterSubscriber(_Event: TNotifyEvent);'}
procedure THAL_Observer.RegisterSubscriber(_Event: TNotifyEvent);
begin
  try
    if IndexOfEvent(_Event) = -1 then
      FListSubscriber.Add(THAL_ObserverItem.Create(_Event));

  except
    on E: Exception do begin
    end;
  end;
end;
{$EndRegion}

{==============================================================================}

{$Region 'procedure THAL_Observer.UnRegisterSubscriber(_Event: TNotifyEvent);'}
procedure THAL_Observer.UnRegisterSubscriber(_Event: TNotifyEvent);
begin
  try
    if IndexOfEvent(_Event) > -1 then begin
      FListSubscriber.Delete(IndexOfEvent(_Event));
    end;
  except
    on E: Exception do begin
    end;
  end;
end;
{$EndRegion}

{==============================================================================}