"could not find implicit value for evidence parameter" with MongoCaseClassField

[Erik Allik]

I recently discovered the rather useful MongoCaseClassField, however, it seems that doing e.g. where(_.status eqs Pending) on it results in the following compilation error:

    could not find implicit value for evidence parameter of type com.foursquare.rogue.BSONType[my.pkg.JobStatus]

Where JobStatus is defined as sealed trait JobStatus with a bunch of case object definitions extending it.

Should this be reported as a bug? And are there any workarounds meanwhile?

Regards,

Erik

[Erik Allik]

OK, it looks like this works:

      implicit object JobStatusIsBSONType extends com.foursquare.rogue.BSONType[JobStatus] {

        override def asBSONObject(v: JobStatus): AnyRef = v.toString

      }

Is my definition of JobStatusIsBSONType appropriate?

However, as far as I can tell, there is no way to generalize this to any ADT because there's no type to define the typeclass instance on—am I right?

Erik

[Jason Liszka]

Hi Erik,

Unless you've implemented specialized serialization/deserialization logic for your case class, rogue isn't going to be able to deserialize it into the right subclass of JobStatus. I would recommend using an enum instead of case objects in this case.

Regards,

Jason

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