[fpc-pascal] Design Patterns Questions

[bsquared]

Hi all,

It has been some time since I have used FPC/Laz.  I was looking for some
information on 'observer pattern' the other day, and I found this
article[1].  I notice that it is a bit old, and it makes me question
whether or not I have made an error following it.

I get an invalid cast error at this code
   (DigitalClock1 as ISubject).Attach(fClockTimer as IObserver);
which is actually flipped and should be
   (fClockTimer as ISubject).Attach(DigitalClock1 as IObserver);

So, my questions ...
  Is the article out of date?
  Are these patterns implemented in the base code?
  And as an aside, what is the state of tiOPF, I could not get it to
  install in Lazarus 1.02.

Thank you.

[1] -  http://blogs.teamb.com/joannacarter/2004/06/30/690
-- 
Regards,
Brian