scalaz-stream consume stream based on computed value

Question

I've got two streams and I want to be able to consume only one based on a computation that I run every x seconds.

I think I basically need to create a third tick stream - something like every(3.seconds) - that does the computation and then come up with sort of a switch between the other two.

I'm kind of stuck here (and I've only just started fooling around with scalaz-stream).

Thanks!

Answer 1

There are several ways we can approach this problem. One way to approach it is using awakeEvery . For concrete example, see here .

To describe the example briefly, consider that we would like to query twitter in every 5 sec and get the tweets and perform sentiment analysis. We can compose this pipeline as follows:

val source = 
    awakeEvery(5 seconds) |> buildTwitterQuery(query) through queryChannel flatMap {
        Process emitAll _ 
    }

Note that the queryChannel can be stated as follows.

def statusTask(query: Query): Task[List[Status]] = Task {
      twitterClient.search(query).getTweets.toList
}

val queryChannel: Channel[Task, Query, List[Status]] = channel lift statusTask

Let me know if you have any question. As stated earlier, for the complete example, see this .

I hope it helps!