Slick 3.0将Rep（绑定）转换为值

Question

I am trying to join two tables using Slicks 3.0 monadic joins like this:

def getInfo(id: Int) = {

  val innerJoin = for {
    a <- tableA
    b <- tableB if a.id === b.s_id
  } yield b.name

  println(innerJoin) // results in Rep(Bind)

  innerJoin.map(println(_)) // results in Rep(Ref @1535257794)
}

Now I want to get the values from the join results. I tried a lot to get the values but it seems to be harder then I imagined. I always get some sort of Rep(Bind) back when I try to print the values (see comments above).

There is also this post which addresses the same problem. I tried the suggested solution which looks like this:

innerJoin.map(c => c).forEach(id =>
  println(id)
)

Which doesn't even compile since forEach is not defined in that place. I don't really know how to proceed here an what to try next. Can someone help me out?

Thanks...

Answer 1

val innerJoin in your code is a slick query which can be extended / modified or turned into a DBIOAction . An action is something that can be executed on a database which will eventually return your results:

val action = innerJoin.result
val results: Future[Seq[String]] = db.run(action)

// finally use map to access your result
results.map(s => s.map(name => ...)  // s is of type Seq[String]

I assumed your for comprehension retuns a String . Therefore the type of val results is Future[Seq[String]] .

Also have a look at http://slick.typesafe.com/doc/3.0.0/dbio.html#executing-database-io-actions