From: Peter <Peter.Vanbroekhoven@...>
Date: 2003-11-28T03:46:55+09:00
Subject: Re: Method wrapping

> And, like i said to Peter, if just the primary method needs a'changin, its a
> good indication that a superclass is needed.

I think I see the cause of the misunderstanding... Your use of method
wrapping is meant to create a complete implementation of a method. Each
wrapper adds extra functionality or changes the signature. A good example
is a basic class that works on bare data, and wrappers are added to pack
and unpack the data, which is really an orthogonal issue. But I would
always have created either adapters for that, or just used helper methods,
although wrapping sounds more convenient to me.

My idea of AOP was a bit different. I wanted to know what AOP was about
and so I attended one of the AspectJ guys' tutorials, and I guess I'm a
bit biased because of their limited implementation. But the main point in
their talk for using AOP was something like logging. When they add an
aspect to a method, it doesn't change signature (a signature change in
Java means method overloading I believe). Also you can add aspects to
methods of other people's classes that don't add functionality, but just
"hack in"  for your own vile purposes. Things like logging or keeping
statistics is a simple example of that (they overuse these examples). And
they are on another level of orthogonality because they don't necessarily
care about the number of arguments or the type of these arguments. Or they
care about just part of that signature, and with some care that can be
left unchanged by e.g., only adding new arguments at the end.

So my conclusion is that there are two kinds of wrappers: those that make
up the base implementation (i.e., the primary method and its required
wrappers) and wrappers added for "meta-tasks". The former ones need to be
treated as a whole, but the latter ones do not - again, if taken care. I
agree that the base implementation must go when the primary method is
changed, but not those "meta-task" wrappers. And I do think that removing
the latter automatically will create some hassle, but for the former I
think that it's OK to do so.

Peter