Scala mongodb : result of query as list

Yes, I agree with the compilation error. I think "collection.find().first().printHeadResult()" is not part of scala driver 1.1.1 release. The current scala driver github which uses this code is "1.2.0-SNAPSHOT" version.

You can get the results using the below code. However, you may experience some async behavior using the below code. Please refer the driver documentation.

val observable: FindObservable[Document] = collection.find();
observable.subscribe ( new Observer[Document] {
  override def onNext(result: Document): Unit = println(result.toJson())
  override def onError(e: Throwable): Unit = println("Failed" + e.getMessage)
  override def onComplete(): Unit = println("Completed")
})

Mongo driver Observables link

This is answered from the best of my current knowledge. I spent a lot of time using casbah and I've recently switched to using the new async scala driver, so there may be more ergonomic ways to do some of this stuff that I don't know yet.

Basically you need to transform the result of the observable and then eventually, you'll probably want to turn it into something that isn't an observable so you can have synchronous code interact with it (maybe, depending on what you're doing).

In the current Mongo Scala API (2.7.0 as of writing this), you might process a list of documents like this:

coll.find(Document("head" -> 1)).map(dbo => dbo.getInteger("head"))

That takes the list of documents where head is equal to one and then applies the map function to convert it from the Document (dbo) into an Int by extracting the "head" element (note this will fall in ugly fashion if there isn't a head field or the field is not an int. There are more robust ways to get values out using get[T]).

You can find a full list of the operations that an Observable supports here: https://mongodb.github.io/mongo-scala-driver/2.7/reference/observables/ under the list of Monadic operators.

The other part is how do you get the good stuff out the Observable because you want to do something synchronous with them. The best answer I have found so far is to dump the Observable into a Future and then calling Await.result on that.

val e = coll.find(Document("head" -> 1)).map(dbo => dbo.getInteger("head"))
val r = Await.result(e.toFuture(), Duration.Inf)
println(r)

That will print out the List[Int] that was created by evaluating the map function for each Document in the Observable.