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scala

Reverse of Future.sequence

I know that a Future.sequence call can convert a List[Future[T]] to a Future[List[T]], but what if I want to go the other way around?

I want to convert a Future[List[T]] into a List[Future[T]].

The reason why I want to do this is as follows:

I send a message to an actor which uses Slick 3 to query a database. The Slick query returns list: Future[List[T]]. If I could convert this list to list: List[Future[T]], then I would be able to do:

list.map(convertToMessage).foreach(m => m pipeTo sender())

So basically I want to convert each record extracted from the DB into a message and then send it to a calling actor.

Solution

  • I don't think this is possible, sorry.

    A Future[List[T]] could complete with an empty list, a list with one element, or any number of elements.

    So if you converted it to a List[Future[T]], how many Futures would the list contain?