Can I use a closure on an event handler (ie, TButton OnClick)

Question

If I try to use a closure on an event handler the compiler complains with :

Incompatible types: \"method pointer and regular procedure\"

which I understand..

Answer 1

In previous Delphi versions you could use a regular procedure as event handler by adding the hidden self pointer to the parameters and hard typecast it:

procedure MyFakeMethod(_self: pointer; _Sender: TObject);
begin
  // do not access _self here! It is not valid
  ...
end;

...

var
  Meth: TMethod;
begin
  Meth.Data := nil;
  Meth.Code := @MyFakeMethod;
  Button1.OnClick := TNotifyEvent(Meth);
end;

I am not sure the above really compiles but it should give you the general idea. I have done this previously and it worked for regular procedures. Since I don't know what code the compiler generates for closures, I cannot say whether this will work for them.