From: Trans <transfire@...>
Date: 2005-10-20T01:41:58+09:00
Subject: Re: [RCR] Cut-based AOP


Eric Mahurin wrote:
> Right now you can actually manually do something like the
> above:
>
> class C
>   def foo;"foo";end
> end
>
> c = C.new
>
> c.foo # => "foo"
>
> class C
>   foo1 = instance_method(:foo)
>   define_method(:foo) { "{"+foo1.bind(self).call+"}" }
> end
>
> c.foo # => "{foo}"
>
> class C
>   foo1 = instance_method(:foo)
>   define_method(:foo) { "["+foo1.bind(self).call+"]" }
> end
>
> c.foo # => "[{foo}]"
>
> Pretty sweet, huh?  I wasn't sure if foo1 kept the previous
> definition until I tried it, but apparently it does.
>
> Maybe just an easier way to do the above is all that is needed.
>  I think the above covers what is really needed for AOP - and
> we already have it.  Just simpler syntax is needed IMO.  No
> extra baggage needs to be added to the class data structures.

Peter covers this well in his repsonse. I just want to point out one
additional thing about using a Cut rather using simple method hooks:
*introduction*. Using Cuts will allow you to conveniently store
information (i.e. state) pertaining to that cut/aspect independent of
the class being cut --an important criterea for good AOP. Presently
class instance vars are what you'd use for this, but as Ruby comes to
support local instance varaibles and/or methods introduction will
become even better.

> I'm not sure why you guys made such a lengthy RCR.  I think I
> have the concept now, but with all of the verbosity, it makes
> it difficult to figure out what you are really proposing.  I
> think a much more concise RCR would have been better.

Granted there are some spots where we could have been a little more
concise. But we wanted to be thurough, much like a white paper, rather
then something just thought up of a few days ago and thrown up. We also
hope the brief overwiew of AOP would be of benefit to those not so
familar with AOP.

Thanks,
T.