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vinoyang commented on FLINK-9221: --------------------------------- [~joshlemer] I think we should not add this method to `SinkFunction` interface, it seems could be implemented in a util class. What's your opinion? [~till.rohrmann] > Add method SinkFunction[A]#contramap[B](f: B => A): SinkFunction[B] > ------------------------------------------------------------------- > > Key: FLINK-9221 > URL: https://issues.apache.org/jira/browse/FLINK-9221 > Project: Flink > Issue Type: Task > Components: DataSet API, DataStream API > Affects Versions: 1.5.0 > Reporter: Josh Lemer > Assignee: vinoyang > Priority: Minor > Labels: flink > > Just like it is very useful to use `DataStream[T]` as a sort of Functor or > Monad with `map`/`flatMap`/`filter` methods, it would be extremely handy to > have a `SinkFunction[A]#contramap[B](f: B => A): SinkFunction[B]` on > `SinkFunctions`, so that you can reuse existing complex sink functions, but > with a different input type. For example: > {code} > val bucketingStringSink: SinkFunction[String] = > new BucketingSink[String]("...") > .setBucketer(new DateTimeBucketer("yyyy-MM-dd-HHmm") > val bucketingIntListSink: SinkFunction[List[Int]] = > bucketingStringSink.contramap[List[Int]](_.mkString(",")) > {code} > For some more formal motivation behind this, > https://typelevel.org/cats/typeclasses/contravariant.html is definitely a > great place to start! -- This message was sent by Atlassian JIRA (v7.6.3#76005)