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Re: R: Re: [aspectj-users] ITD syntax

Ramnivas,

Hmmm... now I think I'm a bit confused.  I haven't used the @DeclareParents annotation, as a matter of fact I wasn't aware it existed until you mentioned it, but if it already uses delegation to accomplish what we're talking about then that's a different story.  If both methods (delegation and direct insertion) already exist within AspectJ I would think that it's less confusing to allow delegation both through annotations and through declarations than to only allow it when using annotations.  It also would imply that the work involved in adding a delegation feature would be a lot less than what I would have expected otherwise.  Another thing to think about....

On Dec 5, 2008, at 1:44 PM, Ramnivas Laddad wrote:

That's quite a good discussion we've had!

There are indeed two different model for implementation for ITDs as
Herman distilled well: the classic member introduction (the current
code-style AspectJ model and Dave's original proposal) and delegation
model (the one implemented in @AspectJ's @DeclareParents and most
likely implementation of my "declare extends" proposal)

So I guess we have two questions to ponder:
1. Do both model make sense. If yes, how to best present them to avoid
confusing users (ss Simone pointed). If not, what should be the status
of @DeclareParents in @AspectJ.
2. (Back to Dave's original question) What is best syntax for "bulk
ITD" i.e. introducing a set of members with a simpler syntax.

-Ramnivas


2008/12/5 Simone Gianni <simoneg@xxxxxxxxxx>:


Hi Herman,
you perfectly got the point. We are moving from IDT to something else, and
that what I felt in the first place without being able to express it with
the clarity you had. I agree on splitting this thread on "A simpler syntax
for IDTs" and "A delegation approach to IDTs".

As long as the simpler syntax for IDTs in involved, I like Dave's
proposal, also because it uses a construct very similar to the "with", which
is present in a number of languages but missing in Java, and many
programmers are already used to it. Also, it simply requires less typing
without changing the semnatics of the IDT.

There can be better ways of doing mixins/IDTs, including the delegation
based ones, but that's another discussion.

Simone

----- Messaggio originale -----
Da: Ichthyostega <prg@xxxxxxxxxxxxxxx>
A: aspectj-users@xxxxxxxxxxx
Posta Inviata: giovedì 4 dicembre 2008 22.42.08 GMT+0100 Europe/Berlin
Oggetto: Re: [aspectj-users] ITD syntax

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Hi Dave,

I'm glad for this discussion because it's helped me in refining how I
think
this would work best.
Same here. I saw your answer just after posting mine.
Probably we are facing a decision on two possible routes to take:

- - provide some convenience for Delegation using AspectJ
- - stick to the ITD semantics but provide a better syntax.

My feeling is we would be best off if we took a clear decision on
one of those routes and don't try to mix them up. Even if we were
able to come with a combined solution, it will confuse people.

Thus, if we go the "Delegation" route, "this" should be really rebound
the moment we are within the scope of the delegate to mean the delegate,
the same way as if all of this was just implemented in plain Java.
OTOH, when going the "ITD" route, the source class (ITDDefaultImpl
or DoSomethingImpl) is rather sort-of a template for code woven into
the target. I.e., at runtime, no class DoSomethingImpl will be loaded.
Then the question remains what should happen with private fields.
Consider, both the class Doer and class DoSomethingImpl may use
a private field with the same name for their implementation.

Hermann





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