Scala macros for nested case classes to Map and other way around

问题

I want to convert any case class to a Map[String,Any] for example:

case class Person(name:String, address:Address)
case class Address(street:String, zip:Int)

val p = Person("Tom", Address("Jefferson st", 10000))
val mp = p.asMap 
//Map("name" -> "Tom", "address" -> Map("street" -> "Jefferson st", "zip" -> 10000))
val p1 = mp.asCC[Person]
assert(p1 === p)

Possible duplications: Here is a question that with reflection answer. Here is a question for (converting from case class to map (without nesting)

I also found how to do it for a case claas without any nested case class inside it, here is the code from here:

package macros
import scala.language.experimental.macros
import scala.reflect.macros.blackbox.Context

trait Mappable[T] {
  def toMap(t: T): Map[String, Any]
  def fromMap(map: Map[String, Any]): T
}

object Mappable {

  implicit def materializeMappable[T]: Mappable[T] = macro materializeMappableImpl[T]

  def materializeMappableImpl[T: c.WeakTypeTag](c: Context): c.Expr[Mappable[T]] = {
    import c.universe._
    val tpe = weakTypeOf[T]
    val companion = tpe.typeSymbol.companion

    val fields = tpe.decls.collectFirst {
      case m: MethodSymbol if m.isPrimaryConstructor => m
    }.get.paramLists.head

    val (toMapParams, fromMapParams) = fields.map { field =>
      val name = field.asTerm.name
      val key = name.decodedName.toString
      val returnType = tpe.decl (name).typeSignature

      (q"$key -> t.$name", q"map($key).asInstanceOf[$returnType]")
    }.unzip



    c.Expr[Mappable[T]] { q"""
      new Mappable[$tpe] {
        def toMap(t: $tpe): Map[String, Any] = Map(..$toMapParams)
        def fromMap(map: Map[String, Any]): $tpe = $companion(..$fromMapParams)
      }
    """ }
  }
}

Also it worth to mention Play Json library and ReactiveMongo Bson library do the same thing, but those project were really big to understand how to do this.

来源：https://stackoverflow.com/questions/31528379/scala-macros-for-nested-case-classes-to-map-and-other-way-around

标签

scala

scala-macros