How do I map my objects correctly to make a list of objects work in mongo + play2

Question

I'm trying to write readers/writers for my case classes after reading:

• https://github.com/sgodbillon/reactivemongo-demo-app/blob/master/app/models/articles.scala

• https://github.com/zenexity/ReactiveMongo/blob/master/driver/samples/BSON.scala

but I'm having trouble in making it work.

I have a leadCategory that can consist of several word objects.

package models

import org.joda.time.DateTime
import reactivemongo.bson._
import reactivemongo.bson.handlers.{BSONWriter, BSONReader}
import reactivemongo.bson.BSONDateTime
import reactivemongo.bson.BSONString

LeadCategory:

case class LeadCategory(
                         id: Option[BSONObjectID],
                         categoryId: Long,
                         categoryName: String,
                         creationDate: Option[DateTime],
                         updateDate: Option[DateTime],
                         words: List[Word]
                         )

object LeadCategory {

  implicit object LeadCategoryBSONReader extends BSONReader[LeadCategory] {
    def fromBSON(document: BSONDocument): LeadCategory = {
      val doc = document.toTraversable
      LeadCategory(
        doc.getAs[BSONObjectID]("_id"),
        doc.getAs[BSONLong]("caregoryId").get.value,
        doc.getAs[BSONString]("categoryName").get.value,
        doc.getAs[BSONDateTime]("creationDate").map(dt => new DateTime(dt.value)),
        doc.getAs[BSONDateTime]("updateDate").map(dt => new DateTime(dt.value)),
        doc.getAs[List[Word]]("words").toList.flatten)
    }
  }

  implicit object LeadCategoryBSONWriter extends BSONWriter[LeadCategory] {
    def toBSON(leadCategory: LeadCategory) = {
      BSONDocument(
        "_id" -> leadCategory.id.getOrElse(BSONObjectID.generate),
        "caregoryId" -> BSONLong(leadCategory.categoryId),
        "categoryName" -> BSONString(leadCategory.categoryName),
        "creationDate" -> leadCategory.creationDate.map(date => BSONDateTime(date.getMillis)),
        "updateDate" -> leadCategory.updateDate.map(date => BSONDateTime(date.getMillis)),
        "words" -> leadCategory.words)
    }
  }

Word:

case class Word(id: Option[BSONObjectID], word: String)

object Word {

  implicit object WordBSONReader extends BSONReader[Word] {
    def fromBSON(document: BSONDocument): Word = {
      val doc = document.toTraversable
      Word(
        doc.getAs[BSONObjectID]("_id"),
        doc.getAs[BSONString]("word").get.value
      )
    }
  }

  implicit object WordBSONWriter extends BSONWriter[Word] {
    def toBSON(word: Word) = {
      BSONDocument(
        "_id" -> word.id.getOrElse(BSONObjectID.generate),
        "word" -> BSONString(word.word)
      )
    }

  }    
}

I'm getting a compile error at:

"words" -> leadCategory.words)

stating:

Too many arguments for method apply(ChannelBuffer)
Type mismatch found: (String, List[Words]) required required implicits.Producer[(String, BsonValue)]

What have I missed? Maybe I have misunderstood the docs...

Answer 1

Try to declare the "Word" implicit objects above the "LeadCategory", if you are putting all of it in the same file.

Scala cannot find the implicit objects for the List[Word] - assuming you are using ReactiveMongo 0.9.