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From "Dale LaBossiere (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (EDGENT-229) Streams and tuple type hierarchies - TStream.cast()?
Date Thu, 02 Mar 2017 15:37:45 GMT

     [ https://issues.apache.org/jira/browse/EDGENT-229?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dale LaBossiere updated EDGENT-229:
-----------------------------------
    Component/s: API

> Streams and tuple type hierarchies - TStream.cast()?
> ----------------------------------------------------
>
>                 Key: EDGENT-229
>                 URL: https://issues.apache.org/jira/browse/EDGENT-229
>             Project: Edgent
>          Issue Type: Improvement
>          Components: API
>            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]



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