The trait as in
(line 296):

trait IdPK extends BaseLongKeyedMapper {
  def primaryKeyField = id
  object id extends MappedLongIndex[MapperType](this.asInstanceOf

i don't know how MapperType works, anyway this is my non-working

trait BaseModel extends BaseLongKeyedMapper {
  object created_by extends MappedLongForeignKey(this, User)
  object created_at extends MappedDateTime(this)
  object updated_by extends MappedLongForeignKey(this, User)
  object updated_at extends MappedDateTime(this)
  object deleted_by extends MappedLongForeignKey(this, User)
  object deleted_at extends MappedDateTime(this)

produces this on every Mapped* object:
BaseModel.scala:14: error: inferred type arguments
[,] do not conform to class
MappedLongForeignKey's type parameter bounds [T <:
net.liftweb.mapper.Mapper[T],O <: net.liftweb.mapper.KeyedMapper

i tried a few things but didn't get behind it. I guess it's because i
also don't know what to do with MapperType like in the IdPK trait.

On Apr 11, 2:09 am, David Pollak <>
> The not overly helpful answer... please look for the IdPK trait... you can
> see how to do stuff like this.
> If you're still stuck, I'll provide a more helpful answer.
> On Fri, Apr 10, 2009 at 4:39 PM, Franz Bettag <> wrote:
> > Hey guys,
> > i had the (simple) idea of creating a trait for these fields:
> >  object created_by extends MappedLongForeignKey(this, User)
> >  object created_at extends MappedDateTime(this)
> >  object updated_by extends MappedLongForeignKey(this, User)
> >  object updated_at extends MappedDateTime(this)
> >  object deleted_by extends MappedLongForeignKey(this, User)
> >  object deleted_at extends MappedDateTime(this)
> > Any ideas how i might do that? I've tried a few things but nothing
> > worked. A simple example would be enought to get me going ;)
> > Thanks in advance
> --
> Lift, the simply functional web framework
> Beginning Scala
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