How to store an Enumeration within a MongoCaseClassField in Lift Record?

Using Lift Record, when I try to retrieve the MongoDB entry below, a NullPointerException is raised when the .asHtml method of MongoCaseClassField is called.

object MyEnumeration extends Enumeration {
  val A, B, C = Value
}

case class MyCaseClass(en: MyEnumeration.Value) 

class MyRecord extends MongoRecord[MyRecord] with MongoId[MyRecord] {
  def meta = MyRecord
  object fail extends MongoCaseClassField[MyRecord, MyCaseClass](this)
}

object MyRecord extends MyRecord with MongoMetaRecord[MyRecord]

However this wor开发者_开发问答ks fine if I use String instead of Enumeration. Is there any way to use enumerations in case class fields or should use a different type of field?

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At the time of writing mongoDB doesn't place nice with scala enums, I use a decorator method as a work around.

Say you have this enum:

object EmployeeType extends Enumeration {
  type EmployeeType = Value
  val Manager, Worker = Value
}

and this mongodb record:

import EmployeeType._
case class Employee(
  id: ObjectId = new ObjectId
)

In your mongoDB, store the integer index of the enum instead of the enum itself:

case class Employee(
  id: ObjectId = new ObjectId,
  employeeTypeIndex: Integer = 0
){
  def employeeType = EmployeeType(employeeTypeIndex); /* getter */
  def employeeType_=(v : EmployeeType ) = { employeeTypeIndex= v.id} /* setter */
}

The extra methods implement getters and setters for the employee type enum.

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I am quite certain that this will only work with native types like String, Int, Float, Double, Boolean, etc, but not Enumerations. I am really certain that this is due to serialization.