Salat parent child relationship

section.scala

package model

import org.joda.time.DateTime
import org.bson.types.ObjectId
import com.novus.salat.annotations._
import com.novus.salat.dao.SalatDAO
import com.mongodb.casbah.Imports._

object Section {
  def subSections(s: Section) = SectionDAO.subSections(s.id)
}
case class Section(@Key("_id") id: ObjectId = new ObjectId,
                   name: String)
object SubSection {
  def questions(s: SubSection) = QuestionDAO.bySubSection(s.id)
}
case class SubSection(@Key("_id") id: ObjectId = new ObjectId,
                      sectionId: ObjectId,
                      name: String)
case class Question(@Key("_id") id: ObjectId = new ObjectId,
                    subSectionId: ObjectId)

object SectionDAO extends SalatDAO[Section, ObjectId](collection = MongoConnection()("salat_db")("sections")) {
  val subSectionColl = new ChildCollection[SubSection, ObjectId](collection = MongoConnection()("salat_db")("subsections"),
    parentIdField = "sectionId") {
    def questions(subSectionId: ObjectId) = QuestionDAO.bySubSection(subSectionId).toList
  }

  def subSections(sectionId: ObjectId) = subSectionColl.findByParentId(sectionId).toList
}

object QuestionDAO extends SalatDAO[Question, ObjectId](collection = MongoConnection()("salat_db")("questions")) {
  def bySubSection(subSectionId: ObjectId) = find(MongoDBObject("subSectionId" -> subSectionId))
}