How do I access the fields of a link-table with Lift Mapper?

问题

From the Lift-Web Mapper model below, how do I access the fields under AssignmentformLink?

object TForm extends TForm with LongKeyedMetaMapper[TForm]

class TForm extends LongKeyedMapper[TForm] with IdPK with ManyToMany {
  def getSingleton = TForm

  object label extends MappedString(this, 40)

  object pattern extends MappedString(this, 200)

  object assignments extends MappedManyToMany(
      AssignmentformLink, AssignmentformLink.assignment, AssignmentformLink.form, TForm)

}

object AssignmentformLink extends AssignmentformLink with LongKeyedMetaMapper[AssignmentformLink] {
  override def dbIndexes = Index(form, assignment) :: super.dbIndexes
}

class AssignmentformLink extends LongKeyedMapper[AssignmentformLink] with IdPK {
  def getSingleton = AssignmentformLink

  object form extends MappedLongForeignKey(this, TForm)

  object assignment extends MappedLongForeignKey(this, Assignment)

  object order extends MappedInt(this)

  object readonly extends MappedBoolean(this)

  object required extends MappedBoolean(this)

  object visible extends MappedBoolean(this)

}

object Assignment extends Assignment with LongKeyedMetaMapper[Assignment]

class Assignment extends LongKeyedMapper[Assignment] with IdPK with ManyToMany {
  def getSingleton = Assignment

  object id_parent extends MappedLong(this)

  object label extends MappedString(this, 40)

  object order extends MappedInt(this)

  object guard extends MappedString(this, 200)

  object forms extends MappedManyToMany(
      AssignmentformLink, AssignmentformLink.assignment, AssignmentformLink.form, TForm)

}

To get an assignmet and the forms linked to it, you do this:

val assignments = Assignments.find(By(Assignment.id, 123))

assignments match {
  case Full(as) => {
    val forms = as.forms
.....

But I have no idea how to navigate to the order, readonly, required... fields under AssignmentformLink.

I realise I can search for the link manually, ie. AssignmentformLink.find(By(form...),By(assignment...)), but this will result in inefficient code and really misses the point of using objects.

I need to be able to navigate from the form to the link table's fields.

回答1:

Don't know if this is the correct approach, but assignments.joins returns a list of the join table records.

来源：https://stackoverflow.com/questions/12843590/how-do-i-access-the-fields-of-a-link-table-with-lift-mapper

标签

scala

lift