CODEWITHSUNDEEP
scalasolrtypes
Gohmz
Gohmz

Reputation: 1286

Scala : Match of parameter Type

I'm making an app which make request in Solr with Scala. Actually, i got 10 case class that I instance after my requests. To made an generic app, I try to use parameter type.

My problem : I have to make a switch on my Paramter Type and it's obv not working (due to erasure).

See my reflexions & pseudo code.:

getItem[Apple](10)

=>

def getItem[T](id : Option[Int]) = {
... // Here I request Solr then i want to create my caseClass from Solr docs.
mapsolr[T].toUseCase(docs) // send solr docs to map
}

Here my mapping :

class mapSolr(docs){
    def toUseCase[T] = {
       // Here i want to be able to make a switch on T
        typeOf[T] match {
        case x if x =:= typeOf[CaseClass1] =>
           blabla // (return List[CaseClass1]
        case x if x =:= typeOf[CaseClass2] =>
           blabla // (return List[CaseClass2]
       }
}

I got the error "No TypeTag available for T". I know its because erasure, but i have no idea how to do.

I just want to be able to test my parameter type ...

Thanks.

Upvotes: 2

Views: 101

Answers (1)

adamwy
adamwy

Reputation: 1239

You need to add TypeTag context bound to T:

import scala.reflect.runtime.universe._

def toUseCase[T: TypeTag] = {
   // Here i want to be able to make a switch on T
    typeOf[T] match {
    case x if x =:= typeOf[CaseClass1] =>
       blabla // (return List[CaseClass1]
    case x if x =:= typeOf[CaseClass2] =>
       blabla // (return List[CaseClass2]
   }
}

You also need to pass TypeTag in generic code that uses this method:

def getItem[T: TypeTag](id : Option[Int]) = {
  ... // Here I request Solr then i want to create my caseClass from Solr docs.
  mapsolr[T].toUseCase(docs) // send solr docs to map
}

Upvotes: 5

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