Question

UPDATE: Changed the samples to reflect my current situation

Fairly new to lift and I am trying to create a model for my application. Since I want to keep things in the spirit of DRY I want to use trait mixins to specify some of the fields in my model. For instance, I have a Person trait which I mixin to my Employee class:

trait Person[T <: LongKeyedMapper[T]] extends LongKeyedMapper[T]{
  self: T =>
  object firstName extends MappedString[T](this, 50)
  object lastName extends MappedString[T](this, 50)
  object civicRegNumber extends MappedString[T](this, 12)
}

class Employee extends IdPK with OneToMany[Long, Employee] with Person[Employee] {
  def getSingleton = Employee

  object contactInfos extends MappedOneToMany(EmployeeContactInfo, EmployeeContactInfo.person) 
}

object Employee extends Employee with LongKeyedMetaMapper[Employee] 

As can be seen I have a contactInfos many to one mapping in the Employee. It looks like:

trait PersonContactInfo[T <: LongKeyedMapper[T],P <: Person[P]] extends LongKeyedMapper[T] {
  self: T =>
  object email extends MappedEmail[T](this, 80)
  def personMeta:P with LongKeyedMetaMapper[P]
  object person extends LongMappedMapper[T,P](this, personMeta)
}

class EmployeeContactInfo extends IdPK with PersonContactInfo[EmployeeContactInfo, Employee] {
  def getSingleton = EmployeeContactInfo
  val personMeta = Employee

}
object EmployeeContactInfo extends  EmployeeContactInfo with LongKeyedMetaMapper[EmployeeContactInfo]

This seems to work, but I would like to move the contactInfos object into my Person trait. However, I can’t figure out how to achieve this… Is it at all possible to inherit OneToMany mappings from traits? Any help welcome!

Answer 1

After a few tries I got this to work by separating the trait which does the OneToMany mapping of Person to PersonContactInfo. This is how it looks now

trait Person[T <: Person[T]] extends LongKeyedMapper[T]{
  self: T =>
  object firstName extends MappedString[T](this, 50)
  object lastName extends MappedString[T](this, 50)
  object civicRegNumber extends MappedString[T](this, 12)
}

trait PersonToPersonContacts[P <: Person[P], PCI <: PersonContactInfo[PCI, P]] extends OneToMany[Long,P] {
  self: P =>
  def contactInfoMeta:LongKeyedMetaMapper[PCI] with PCI
  object contactInfos extends MappedOneToMany(contactInfoMeta, contactInfoMeta.person)
}

class Employee extends IdPK with Person[Employee]  with PersonToPersonContacts[Employee, EmployeeContactInfo] {
  def getSingleton = Employee
  override def contactInfoMeta = EmployeeContactInfo
}
object Employee extends Employee with LongKeyedMetaMapper[Employee] 

and my PersonContactInfo now looks like:

trait PersonContactInfo[T <: LongKeyedMapper[T],P <: Person[P]] extends LongKeyedMapper[T] {
  self: T =>
  object email extends MappedEmail[T](this, 80)
  def personMeta:P with LongKeyedMetaMapper[P]
  object person extends LongMappedMapper[T,P](this, personMeta)
}

class EmployeeContactInfo extends IdPK with PersonContactInfo[EmployeeContactInfo, Employee] {
  def getSingleton = EmployeeContactInfo

  val personMeta = Employee

}
object EmployeeContactInfo extends  EmployeeContactInfo with LongKeyedMetaMapper[EmployeeContactInfo]

Still not sure if this is the way to solve this, but ity does the job 🙂