Hi Neale
Thanks for the reply and the useful info. I'll give what you suggested a try.
One thing I should point out though is that Fish and Mammal are both concrete
classes, not interfaces as your example suggests. Do you think that will cause
a problem? To make things even more interesting, and this is where my
simplified example starts to break down, Fish actually extends Mammal too (!).
It's actually more like this in real life:
Current Situation
----------------------
1) OrderClass <----------- AbstractWorkflowClass
<------------------------------------------- DomainClass
2) InvoiceClass <---------------------------------------------
DomainWithExtraStuffClass <-- DomainClass
I need to modify InvoiceClass so it also extends AbstractWorkFlowClass, and
make AbstractWorkflowClass extend DomainWithExtraStuffClass *but only* when
dealing with InvoiceClass instances. When I'm dealing with OrderClass,
AbstractWorkflowClass should still extend the base DomainClass.
New Situation
------------------
1) OrderClass <----------- AbstractWorkflowClass
<--------------------------------------------------- DomainClass
2) InvoiceClass <--------- AbstractWorkflowClass <-------
DomainWithExtraStuffClass <----- DomainClass
Which obviously isn't normally possible in Java, which is why I thought an ITD
might be the way forward. Incidentally, I was hoping I could change
AbstractWorkflowClass to extend DomainWithExtraStuffClass but apparently (and I
can understand the concerns) we can't do this because it would mean making all
the functionality in DomainWithExtraStuffClass available to OrderClass (and the
many other classes that extend it - it's a big system)
You've given me something to go on and it sounds promising, so thanks again for
the assistance.
Richard
From: Neale Upstone
Sent: Thursday, October 14, 2010 9:38 PM
To: aspectj-users@eclipse.org
Subject: Re: [aspectj-users] Can inter-type declarations do this?
It sounds like what you want is to have Dog extend AbstractCreature, Mammal,
and Shark extend AbstractCreature,Fish
In the world of ITDs I think what you're looking to do is to have the
abstractness of AbtractCreature fulfilled by either Mammal or Fish.
YOu should be able to do:
class Dog extends AbstractCreature implements Mammal {
}
And then declare the implementations for the abstract methods in
AbstractCreature as ITDs in both Mammal and Fish:
something like:
public aspect MammalImpl {
public void Mammal.methodThatsAbstractInAbstractCreature() {
//method impl;
}
}
On 14/10/2010 17:08, Richard Gundersen wrote:
Hi
I'm struggling with a problem that I *think* AspectJ might be able to help me
with, but I'm not sure so I was hoping someone could give me some advice.
I want to be able to change the class that a certain class' superclass
extends, if that makes sense? So (in terms that I understand) I might have Dog,
which extends AbstractCreature, which in turn extends Mammal.
However alongside Dog, I now want to add 'Shark' which I still want to extend
AbstractCreature (because it has some useful functionality). But, this time, I
want to change the class that AbstractCreature extends to 'Fish', rather than
Mammal. Like this:
Dog <-- AbstractCreature <-- Mammal
Shark <-- AbstractCreature <-- Fish
So basically if AbstractCreature is being subclasses by a dog, it should
extend Mannal, or if by Shark, it should extend Fish.
I'm hoping there's a magical inter-type declaration annotation (or even
better a Spring/AspectJ annotation, something like @DeclareParents perhaps)
that I can add to both Dog and Shark.
I would really appreciate any help anyone can give me on this. My real world
example is some really complex code that I don't want to duplicate/mess with
too much, so AOP would seem to be a perfect solution.
If its of any use, in my real world example, Shark extends Fish directly, but
I need to modify it so Shark now extends AbstractCreature, and then
(ultimately) Fish, not Mammal.
Thanks
Richard
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