通用子类的scala TypeTag

Question

I have a case class Document with a generic type Parameter. Now I want get at runtime the TypeParamater types.

I did not found a way.

def toHtml[T <: DocumentType](doc: Document[T])(variableSubstitution: String => String ): String = {
doc match {
      case _ : Document[UnStructured] =>
      case _ => //
    }
}

My Document Class:

final case class Document[T <: DocumentType](chapterList: SortedSet[_ <: ChapterTrait[T]],
                                             uniqueId: UUID = UUID.randomUUID(),
                                             createDate: DateTime = DateTime.now(),
                                             lastEdit: DateTime = DateTime.now(),
                                             title: String = "",
                                             version: Double = 1.0,
                                             designSetting: DocumentDesignSettingTrait = DocumentDesignSetting(),
                                             paperFormat: PaperFormat = A4,
                                             headerList: List[PageMark] = Nil,
                                             footerList: List[PageMark] = Nil,
                                             preContent: PreContent = PreContent(),
                                             postContent: PostContent = PostContent(),
                                             author: Author = Author() ) {

}

Now the types for document

sealed abstract class DocumentType

sealed abstract class StructuredDocumentType extends DocumentType

sealed abstract class SemiStructured extends StructuredDocumentType
//case object SemiStructured extends SemiStructured

sealed abstract class Structured extends StructuredDocumentType
//case object Structured extends Structured

sealed trait UnStructured extends DocumentType
//case object UnStructured extends DocumentType

I want now find out which type parameter is bounded at doc.

Someone any indea?

Answer 1

I'm newish to Scala but I think what you're looking for in your match is something like the following:

import scala.reflect.runtime.universe.{TypeTag, typeOf}

def toHtml[T <: DocumentType](doc: Document[T])(variableSubstitution: String => String )(implicit tag: TypeTag[T]): String = typeOf[T] match {
  case t if t =:= typeOf[UnStructured] => // ...
  case t if t =:= typeOf[SemiStructured] => // ...
  case _ => // ...
}

I've had lots of luck using the reflection API when I've programmed with generics in the past. Let me know if this helps!