scala - Fail to use Manifest to to extract data with json4s -

i have simple function takes string json , extract case class, looks this:

type extractiontype  implicit def extractionmanifest: manifest[extractiontype]   def myexctractionfunc: list[finalmodel] = {  val mylist: list[finaltype] = parse(response.body).extract[extractiontype]  ...  } 

now, theres 2 services (in different classes) using function , each 1 implementing extractiontype , extractionmanifest differently.

but, 1 service works perfect, , other im getting error:

the future returned exception of type: org.json4s.package$mappingexception, message: unknown error.

(myexctractionfunc using futures , more complex stuff simplified it, why error mention future)

the implementation of service fail extract is:

case class  person (name: string, age: int)  override type extractiontype = list[person]  override implicit val inmanifest = manifest.classtype[list[person]](classof[list[person]]) 

the service succeed looks this:

case class animal(kindofanimal: string, age: int)  case class jungleobjects(animals: list[animal])   override type extractiontype = jungleobjects    override implicit val inmanifest = manifest.classtype[jungleobjects](classof[jungleobjects]) 

does can see why 1 working , other not?

i had use case classes in projects separate things, simplified code question won't annoying :)

thanks!