From: Clemens Hintze <c.hintze@...>
Date: 1999-01-15T10:51:06+00:00
Subject: [ruby-talk:00186] Re: finalizer help please

Hmm. Here seems to exit two problems. 

First Ruby assume that DestroyWindow is a method. Is it possible that
the contents of WINGKRUser are encapsulated via module <name> ... end?
If so you should call the function like that
<name>::DestrowWindow(@handle) or <name>.DestroyWindow(@handle).
Alternativ you could also perform a include <name> after the require.

The second should be, that your destructor should never be called, I
think. I have done a very similar approach for my first module. Matz
has told me then, that my destructor helds a pointer to self, means to
my instance I wish to finalize! Due to that fact the GC will never
recognize my instance as unused. So no finalization should take place,
as there is a pointer to my instance all the time. And for GC
pointer-to-instance means "used".

Furthermore I wonder, why you deliver self to the
WinControl.destructor call. You assume, that you points to the current
instance as you use @handle. But you have also delivered the current
instance to the obj variable. That is, you should now have too much
two pointers to the current instance. If no other variable within he
Ruby interpreter points to that instance, at least self and obj will
point to it. No chance for GC!

So if my explanation was true and I remember right, you could rewrite
your destructor as follow:

def WinControl.destructor ( handle )
  lambda {
  require 'WINGKRUser32'

  if handle != 0 then
   if <name>::DestroyWindow ( handle ) != 0 then
    print "\n\r Destroyed: ", handle
   else
    print "\n\r Could NOT destroy: ", handle
   end
  end
  }
end

Here, no pointer to self should be held. So the GC can detect that
your instance is unused.

I hope the explanaitions was correct.

Ciao,
Cle.