[webbeans-dev] removeObserver type

[Gavin King]

well,

(1) an Observer could be registered multiple times with diff event bindings
(2) adding a type variable doesn't help you, since it just gets erased
at runtime

You can't do T.class in Java :-)

On Wed, May 27, 2009 at 1:06 PM, Clint Popetz <cpopetz at gmail.com> wrote:
> Now that I'm thinking about it, I wrote "the observer should be removed for
> all events for which it is registered" but because addObserver() is typed to
> Observer<T>, and because you can't implement the same interface twice (even
> with different parameterizations) any given instance can only be registered
> once.   Well, it could be registered more than once, but the implementation
> (and possibly the spec) could prohibit that, because it's meaningless.
>
> In that case, I have no problem with the semantics of removeObserver.  But
> the <?> means I'd have to rewrite a lot of observer storage/lookup code, and
> it's not symmetric with addObserver(), so I wonder what the advantage of the
> wildcard is.
>
> -Clint
>
>
> On Wed, May 27, 2009 at 2:35 PM, Gavin King <gavin.king at gmail.com> wrote:
>>
>> yes, that's what it means, though I must admit that when I made that
>> change it was not totally clear to me that it was the right thing to
>> do :-/
>>
>> Probably needs a bit more discussion...
>>
>> On Wed, May 27, 2009 at 11:59 AM, Clint Popetz <cpopetz at gmail.com> wrote:
>> > Hi,
>> >
>> > The spec defines BeanManager.removeObserver to have a wildcard type:
>> >
>> > public void removeObserver(Observer<?> observer);
>> >
>> > and says "The container must stop sending event notifications to the
>> > deregistered observer."  Does that sentence, taken with the wildcard
>> > type,
>> > imply that the observer should be removed for all events for which it is
>> > registered?  Currently ManagerImpl implements storage of observers as a
>> > map
>> > from EventType -> Observer, which means removal of an observer without
>> > knowing its event type would be linear in # observers, unless I change
>> > the
>> > implementation.
>> >
>> > Thanks,
>> > -Clint
>> >
>> >
>> > --
>> > Clint Popetz
>> > http://42lines.net
>> > Scalable Web Application Development
>> >
>> > _______________________________________________
>> > webbeans-dev mailing list
>> > webbeans-dev at lists.jboss.org
>> > https://lists.jboss.org/mailman/listinfo/webbeans-dev
>> >
>> >
>>
>>
>>
>> --
>> Gavin King
>> gavin.king at gmail.com
>> http://in.relation.to/Bloggers/Gavin
>> http://hibernate.org
>> http://seamframework.org
>
>
>
> --
> Clint Popetz
> http://42lines.net
> Scalable Web Application Development
>



-- 
Gavin King
gavin.king at gmail.com
http://in.relation.to/Bloggers/Gavin
http://hibernate.org
http://seamframework.org