Making independent Slick queries inside of single Play action - scala

Question

I have async Play Action, that retrieves data from the datbase, using Slick. And Slick, obviously, uses Futures to avoid blocking:
def show(id: Long) = Action.async {
db.run(entities.filter(_.id === id).result.headOption).map {
case None => templateFor("NEW_OBJECT")
case Some(x) => Ok(x)
}
def templateFor(code: String): Future[Result] = {
db.run(templates.filter(_.code === code).result.headOption).map {
case None => InternalServerError("No template")
case Some(x) => Ok(x)
}
}
The problem is that call to templateFor() returns Future, so the whole Action returns Future[Future[Result]] which is not what expected by Play. So, i would like to get rid of that nested Future. The simple way to do it is to Await for it's completion, but i would like to avoid unnecessary blocking. It would be nice if i would be able to take Future[Result] produced by templateFor() function and return it intact from my Action, thus replacing the outer Future with it.

Answer 1

You can use flatMap for that,
For any monandic strutcture such as Future[T], flatMap takes a function of type T => SomeOtherMonad[K], applies that function on all elements if monad and then flattens them to gives you Future[K].
def show(id: Long) = Action.async {
db.run(entities.filter(_.id === id).result.headOption).flatMap {
case None => templateFor("NEW_OBJECT")
case Some(x) => Future(Ok(x))
}
def templateFor(code: String): Future[Result] =
db.run(templates.filter(_.code === code).result.headOption).map {
case None => InternalServerError("No template")
case Some(x) => Ok(x)
}
}