Question

Further to this post whose accepted answer remains very cryptic:

@Button1.OnClick := pPointer(Cardinal(pPointer( procedure (sender: tObject) begin ((sender as TButton).Owner as TForm).Caption := 'Freedom to anonymous methods!' end )^ ) + $0C)^;

I wonder wether it is possible to devise a simplest and elegant way akin to:

Button.OnClick :=
                    AnonProc2NotifyEvent (
                    procedure (Sender: TObject)
                    begin
                      ((Sender as TButton).Owner as TForm).Caption := 'Freedom to anonymous methods!'
                    end
                      );

so as to attain the same purpose and where AnonProc2NotifyEvent is a method of the owner of Button with the following signature:

TOwnerOfButton = class(TForm)
  Button: TButton;
  ...
private
  ...
protected
  function AnonProc2NotifyEvent(aProc: TProc<TObject>): TNotifyEvent;
public
  ...
end;

Is that feasible and if so how to implement it ?

Answer 1

This will do the job readily enough:

type
  TNotifyEventWrapper = class(TComponent)
  private
    FProc: TProc<TObject>;
  public
    constructor Create(Owner: TComponent; Proc: TProc<TObject>);
  published
    procedure Event(Sender: TObject);
  end;

constructor TNotifyEventWrapper.Create(Owner: TComponent; Proc: TProc<TObject>);
begin
  inherited Create(Owner);
  FProc := Proc;
end;

procedure TNotifyEventWrapper.Event(Sender: TObject);
begin
  FProc(Sender);
end;

function AnonProc2NotifyEvent(Owner: TComponent; Proc: TProc<TObject>): TNotifyEvent;
begin
  Result := TNotifyEventWrapper.Create(Owner, Proc).Event;
end;

The Owner parameter in AnonProc2NotifyEvent is so that the lifetime of the wrapper object can be managed. Without something like that you would leak instances of TNotifyEventWrapper.

Pass as Owner, the component to which you are connecting the event. For example:

Button1.OnClick := AnonProc2NotifyEvent(
  Button1,
  procedure(Sender: TObject)
  begin
    (Sender as TButton).Caption := 'Clicked';
  end
);

So, when the button is destroyed, the TNotifyEventWrapper will also be destroyed. The wrapper object must live at least as long as the object to whose events it is associated. And so the choice of Button1 as the owner is the natural and obvious one.