Tin Ng Tin Ng - 1 year ago 72
JSON Question

How to get type declared from Iterable in Scala?

I am wondering if there is way to get the declared type in the underlying Iterable as in:

var string: Seq[String] => I want something to return String
var int: Seq[Int] = _ => I want something to return Int
var genericType: Seq[A] => I want to return A

I need to know the class of these types so I can use the underlying Json Library to deserialize the json string into this type.

Something like

def fromJson[A](jsonString: String)(implicit tag: TypeTag[A]): A = ???


Answer Source

I might have not provided enough information in my question. Anyway, I found out the answer.

In order to retrieve a class from a generic type I had to do the following

import scala.reflect.runtime.universe._
val m = runtimeMirror(getClass.getClassLoader)
def myMethod[A](implicit t: TypeTag[A]) = {
  val aType = typeOf[A]
  aType.typeArgs match {
     case x: List[_] if x.nonEmpty => m.runtimeClass(x.head)
     case x: List[_] if x.isEmpty => m.runtimeClass(aType)
scala> myMethod[Seq[String]]
res3: Class[_] = class java.lang.String

scala> myMethod[Seq[Int]]
res4: Class[_] = int

scala> case class Person(name: String)
defined class Person

scala> myMethod[Seq[Person]]
res5: Class[_] = class Person

scala> myMethod[Person]
res6: Class[_] = class Person

I can then provide this class to the underlying library to do its job. Thanks

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