[
https://issues.apache.org/jira/browse/QUARKS-229?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15375249#comment-15375249
]
Dale LaBossiere commented on QUARKS-229:
----------------------------------------
djd: Any reason why the original streams were just not declared with the base
type?
dlaboss: Yes. Imagine there are both base-type analytics and derived-type
analytics.
djd:Would it help if union signature was changed to:
TStream<T> union(TStream<? extends T> other);
dlaboss: It wouldn’t directly/completely. i.e., logically one wants:
TStream<Base> sB = sDerived1.union(sDerived2); // but Derived2 derives
from Base not Derived1
With only that union change, one still has to:
TStream<Base> sB = sDerived1 ??? some cast-ish thing is needed
sB = sB.union(sDerived2);
With some-cast there’s no need to change union, though that might still be
useful.
By “larger” [more than union] I was thinking of something like someone already
wrote doBaseAnalytics(TStream<Base>).
Shame on them for not enabling future reuse by writing
doBaseAnalytics(TStream<? extends Base>)?
Imagine at the time it was written there weren’t any derived classes / it
wasn’t imagined there would be any.
Some cast-ish thing addresses that case too.
Related, a collection of Base oriented “functions" may have been written.
Those and the methods that use them would have to be adjusted too? Function<?
extends Base, String> baseKeyFn
(maybe that’s related to the publish() you mentioned. e.g.,
KafkaPublisher.publish())
> Streams and tuple type hierarchies - TStream.cast()?
> ----------------------------------------------------
>
> Key: QUARKS-229
> URL: https://issues.apache.org/jira/browse/QUARKS-229
> Project: Quarks
> Issue Type: Improvement
> Reporter: Dale LaBossiere
> Priority: Minor
>
> In a real use case there were two different types of sensors that had
> a common interface/info to be analyzed. It took a bit to figure out how to
> deal with this. It certainly wasn't convenient.
> Imagine the tuple type hierarchy:
> class Base {};
> class Derived1 extends Base {};
> TStream<Derived1> sDerived1 = ...; // ingest
> class Derived2 extends Base {};
> TStream<Derived2> sDerived2 = ...; // ingest
> TStream<Base> sBase = sDerived1.union( sDerived2 );
> doAnalytics( sBase );
> The union() gets a compilation error because TStream<Derived*> doesn't extend
> TStream<Base>. Std java generics stuff. A straightforward cast doesn't
> work; it requires a bit more convoluted casting.
> [I'll capture the essence of a thread on the dev list for this below]
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
