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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. [WayBackpragmatic_programmer wrote some cool code at [WayBackdelphi – 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

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

  1. jpluimers said

    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.

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