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delphi – VCL events with anonymous methods – what do you think about this implementation? – Stack Overflow

Posted by jpluimers on 2017/10/19

A long time ago, Pablo Vizcay a.k.a. [WayBack] pragmatic_programmer wrote some cool code at [WayBack] delphi – VCL events with anonymous methods – what do you think about this implementation? – Stack Overflow.

I still think it’s a very neat solution to bind method references to events.

type
  TNotifyEventDispatcher = class(TComponent)
  protected
    FClosure: TProc<TObject>;

    procedure OnNotifyEvent(Sender: TObject);
  public
    class function Create(Owner: TComponent; Closure: TProc<TObject>): TNotifyEvent; overload;

    function Attach(Closure: TProc<TObject>): TNotifyEvent;
  end;

implementation

class function TNotifyEventDispatcher.Create(Owner: TComponent; Closure: TProc<TObject>): TNotifyEvent;
begin
  Result := TNotifyEventDispatcher.Create(Owner).Attach(Closure)
end;

function TNotifyEventDispatcher.Attach(Closure: TProc<TObject>): TNotifyEvent;
begin
  FClosure := Closure;
  Result := Self.OnNotifyEvent
end;

procedure TNotifyEventDispatcher.OnNotifyEvent(Sender: TObject);
begin
  if Assigned(FClosure) then
    FClosure(Sender)
end;

end.

And this is how it’s used for example:

procedure TForm1.FormCreate(Sender: TObject);
begin    
  Button1.OnClick := TNotifyEventDispatcher.Create(Self,
    procedure (Sender: TObject)
    begin
      Self.Caption := 'DONE!'
    end)
end;

–jeroen

This entry was posted on 2017/10/19 at 06:00 and is filed under Delphi, Delphi 10 Seattle, Delphi 10.1 Berlin (BigBen), Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Delphi XE5, Delphi XE6, Delphi XE7, Delphi XE8, Development, Software Development. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

One Response to “delphi – VCL events with anonymous methods – what do you think about this implementation? – Stack Overflow”

  1. jpluimers's avatar

    jpluimers said

    2017/10/19 at 11:16

    Via G+: https://plus.google.com/+JeroenPluimers/posts/HgeCrVYT3SH

    Lars Fosdal
    The problems occur when the capture contains references that change. Something that will not show as a hint or warning.

    Reply

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