Collecting document fields to an array from Mongo DB in Scala

Question

So I have a collection of news articles scored by page views from Mongo DB that I query like this:

// To directly connect to the default server localhost on port 27017
val mongoClient: MongoClient = MongoClient("mongodb://localhost:27017/")
val database: MongoDatabase = mongoClient.getDatabase("Posts")
var collection: MongoCollection[Document] = database.getCollection("news")

collection.find(equal("id","id123")).limit(5).subscribe((doc: Document)=>println(s"${doc.get("views")}"))

This prints:

Some(BsonInt32{value=66043})
Some(BsonInt32{value=66306})
Some(BsonInt32{value=66336})
Some(BsonInt32{value=66365})
Some(BsonInt32{value=66384})

So now I want to collect all of those values into an array, which I have tried to do via this line of code:

var scores = collection.find(equal("id","id123")).limit(5).subscribe((doc: Document)=>doc.get("score").map(_.asInt32().getValue).collect())

But the .collect() does not work.

What is the best way to turn the Mongo field into an array of Ints?

Answer 1

I figured out a solution, though I don't completely understand it:

import org.mongodb.scala._
import org.mongodb.scala.model.Filters._
import org.mongodb.scala.model.Projections._

object main extends App {
  //Connect to Mongo Client and DB
  val mongoClient: MongoClient = MongoClient("mongodb://localhost:27017/")
  val database: MongoDatabase = mongoClient.getDatabase("MyDatabase")

  //Get Collection
  val collection: MongoCollection[Document] = database.getCollection("collectionName")

  //Returns the object with specified fields in projection 
  //as a Future observable containing MongoDB Documents
  val collScores = collection.find(equal("id","id123")).limit(5).projection(fields(include("id", "score", "time"), excludeId()))

  //Maps the document fields to tuples and converts them 
  //to non BSon values since they are easier to work with 
  //than future observables.
  val listMapScores = collScores.map(doc=>(doc("id").asString.getValue,doc("score").asInt32.getValue,doc("time").asDouble.getValue)).collect().results().head 

}

I am not sure why you need to do both results() and then head in the last line. If you don't take the head you end up with a Seq[Seq(String,Int)]]. From what I can tell the future observable contains the same values regardless of if you take the head or the Nth term in the series.