CODEWITHSUNDEEP
scalareflection
seawolf
seawolf

Reputation: 203

How to reflect scala class instance?

Assuming the following code:

package my.package

case class ExampleCaseClass(s: String, i: Int, ...)
object ExampleCaseClass {
  val instance = ExampleCaseClass("number", 5, ...)
}

how can I extract class info and data using Scala reflection if the only reference is a string, say my.package.ExampleCaseClass.instance or something along these lines?

In other words, I want to have a function getInfo: String => String which does, say, the following:

getInfo("my.package.ExampleCaseClass.instance") =
  "ExampleCaseClass ( s: number, i: 5, ... )"

Upvotes: 0

Views: 212

Answers (1)

pme
pme

Reputation: 14803

This uses Java Class.forName:

def getInfo(className: String = "finnova.bpf.report.entity.DocumentBarcode") = { 
  val fields =
  Class.forName(className).getDeclaredFields
    .map(f => s"${f.getName}: ${f.getType.getSimpleName}")
    .mkString("(", ", ", ")")
  s"$className$fields"
}

This uses scala.reflect

import scala.reflect._

def getInfo(className: String = "finnova.bpf.report.entity.DocumentBarcode") = { 
  val classSymbol = runtime.currentMirror.classSymbol(Class.forName(className))
  val primCtor = classSymbol.info.decls.find(m => m.isMethod && m.asMethod.isPrimaryConstructor).get
  val fields = primCtor.typeSignature.paramLists.head
  .map(f => s"${f.name}: ${f.info.resultType}").mkString("(", ", ",")")

  s"$className$fields"
}

This is a bit more involved, but you get much more information. Here is a nice blog that gets you started: https://medium.com/@giposse/scala-reflection-d835832ed13a

Upvotes: 1

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