ReactiveMongo: How to convert a BSONArray to List[String]

Question

Given the following BSONDocument...

val values = BSONDocument("values" -> BSONArray("one", "two", "three"))

How do I convert it to a List? I've tried this...

values.getAs[List[String]]("values").getOrElse(List.empty))

... but it doesn't work - I always get List.empty.

Am I missing something?

EDIT

OK... I think it is worth describing the real case. I ran the distinct command and this was the result:

values: {
  values: [
    0: BSONObjectID("55d0f641a100000401b7e454")
  ],
  stats: {
    n: BSONInteger(1),
    nscanned: BSONInteger(1),
    nscannedObjects: BSONInteger(1),
    timems: BSONInteger(0),
    cursor: BSONString(BtreeCursor projectId_1)
  },
  ok: BSONDouble(1.0)
}

I need to transform values to a Scala List[String] like this:

List("55d0f641a100000401b7e454")

Print the document `values` to check it: `println(s"values: ${BSONDocument pretty values}")` — cchantep, Aug 23 '15 at 17:28
The element type not being `BSONString` but `BSONObjectID`, the array cannot be read as `List[String]` but as `List[BSONObjectID]`. — cchantep, Aug 23 '15 at 19:13

score 0 · Accepted Answer · answered Aug 24 '15 at 18:04

Here is my solution. First, I've defined a BSONReader[BSONValue, String] like this...

package object bsonFormatters {

    implicit object BSONValueStringReader extends BSONReader[BSONValue, String] {

     def read(bson: BSONValue) = bson match { 
      case oid: BSONObjectID => oid.stringify 
    }
}

... and then just imported it in my companion object like this:

import reactivemongo.bson.{BSONString, BSONDocument}
import reactivemongo.core.commands.{CommandError, BSONCommandResultMaker, Command}

case class Distinct(
  collectionName: String,
  field: String,
  query: Option[BSONDocument] = None
) extends Command[Seq[String]] {

  override def makeDocuments = BSONDocument(
    "distinct" -> BSONString(collectionName),
    "key" -> field,
    "query" -> query
  )

  val ResultMaker = Distinct
}

object Distinct extends BSONCommandResultMaker[Seq[String]] {

  import bsonFormatters._ // this makes the trick

  def apply(document: BSONDocument) = CommandError.checkOk(
    document,
    Some("distinct")
  ).toLeft(
    document.getAs[List[String]]("values").getOrElse(List.empty)
  )
}

I hope it helps.

ReactiveMongo: How to convert a BSONArray to List[String]

1 Answers1