How to check if two events are pointing to the same procedure in Delphi?

Question

Say I have a Button1.OnClick event linked to Button1Click procedure. I also have Button2.OnClick linked to some other procedure. How do I check that both events are linked t

Answer 1

I know this is an old question...but here's my 2cents...

This is answer is similar to Nat's but doesn't limit us to only TNotifyEvents...and answers David's question of how to do this with out it being a hack...

function CompareMethods(aMethod1, aMethod2: TMethod): boolean;
begin
  Result := (aMethod1.Code = aMethod2.Code) and
            (aMethod1.Data = aMethod2.Data);
end; 

I use it like so

procedure TDefaultLoop.RemoveObserver(aObserver: TObject; aEvent: TNotifyEvent);
var
  a_Index: integer;
begin
  for a_Index := 0 to FNotifyList.Count - 1 do
    if Assigned(FNotifyList[a_Index]) and
     (TNotify(FNotifyList[a_Index]).Observer = aObserver) and
      CompareMethods(TMethod(TNotify(FNotifyList[a_Index]).Event), TMethod(aEvent))     then
begin
  FNotifyList.Delete(a_Index);
  FNotifyList[a_Index] := nil;
end;

Also a quick and dirty demonstration

procedure TForm53.Button1Click(Sender: TObject);
var
  a_Event1, a_Event2: TMethod;
begin
  if Sender is TButton then
  begin
     a_Event1 := TMethod(Button1.OnClick);
     a_Event2 := TMethod(Button2.OnClick);
    if CompareMethods(TMethod(TButton(Sender).OnClick), a_Event1) then
       ShowMessage('Button1Click Same Method');
    if CompareMethods(TMethod(TButton(Sender).OnClick), a_Event2) then
       ShowMessage('Button2Click Same Method');
  end;
end;


procedure TForm53.Button2Click(Sender: TObject);
var
  a_Event1, a_Event2: TMethod;
begin
  if Sender is TButton then
  begin
     a_Event1 := TMethod(Button1.OnClick);
     a_Event2 := TMethod(Button2.OnClick);
    if CompareMethods(TMethod(TButton(Sender).OnClick), a_Event1) then
       ShowMessage('Button1Click Same Method');
    if CompareMethods(TMethod(TButton(Sender).OnClick), a_Event2) then
       ShowMessage('Button2Click Same Method');
  end;
end;