Dave! Gracias por estar interesado en la nueva reflexión. Los primeros usuarios han impulsado el proceso de desarrollo de la reflexión y las macros en gran medida, y estoy muy feliz de ser parte de nuestra increíble comunidad.
Antes de responder a su pregunta, me gustaría comenzar con un descargo de responsabilidad. En 2.10.0-M4 acabamos de sentar las bases de la API de reflexión de Scala. Todavía está caliente fuera de la prensa, por lo que los documentos son muy escasos y la API no está exactamente plagada de comodidades. Funciona, pero requiere pruebas y comentarios. Claro, jugar con las API previas a la publicación es problemático, pero siempre estoy aquí para ayudarlo.
Hasta ahora tenemos un borrador de lo que en el futuro se convertirá en el reflejo SIP: https://docs.google.com/document/d/1Z1VhhNPplbUpaZPIYdc0_EUv5RiGQ2X4oqp0i-vz1qw/edit#heading=h.pqwdkl1226tc. Puede leerlo de inmediato o puede leer mi respuesta a continuación.
trait Base {
def companion: MetaBase = {
// runtime reflection is typically done
// by importing things from scala.reflect.runtime package
import scala.reflect.runtime._
// the new Scala reflection API is mirror based
// mirrors constitute a hierarchy of objects
// that closely follows the hierarchy of the things they reflect
// for example, for a class you'll have a ClassMirror
// for a method you'll have a MethodMirror and so on
// why go the extra mile?
// because this provides more flexibility than traditional approaches
// you can read more about mirror-based designs here:
// https://dl.dropbox.com/u/10497693/Library/Computer%20Science/Metaprogramming/Reflection/mirrors.pdf
// https://dl.dropbox.com/u/10497693/Library/Computer%20Science/Metaprogramming/Reflection/reflecting-scala.pdf
// bottom line is that to do anything you will need a mirror
// for example, in your case, you need a ClassMirror
// remember I said that mirrors provide more flexibility?
// for one, this means that mirror-based reflection facilities
// might have multiple implementations
// in a paper linked above, Gilad Bracha muses over a runtime
// that loads things remotely over the network
// in our case we might have different mirrors for JVM and CLR
// well, anyways
// the canonical (and the only one now) implementation of the mirror API
// is Java-based reflection that uses out of the box classloaders
// here's its root: https://github.com/scalamacros/kepler/blob/9f71e9f114c10b52350c6c4ec757159f06e55daa/src/reflect/scala/reflect/api/Mirrors.scala#L178
// yeah, right, I've just linked a source file from trunk
// we'll have Scaladocs for that soon, but for now take a look
// this file is interfaces-only and is heavy on comments
// to start with Java-based reflection implementation you need a classloader
// let's grab one and instantiate the root mirror
// btw, the same effect could be achieved by writing
// `scala.reflect.runtime.currentMirror`
val rootMirror = universe.runtimeMirror(getClass.getClassLoader)
// now when we've finally entered the reflective world
// we can get the stuff done
// first we obtain a ClassSymbol that corresponds to the current instance
// (ClassSymbols are to Scala the same as Classes are to Java)
var classSymbol = rootMirror.classSymbol(getClass)
// having a Scala reflection entity
// we can obtain its reflection using the rootMirror
val classMirror = rootMirror.reflectClass(classSymbol)
// now we just traverse the conceptual hierarchy of mirrors
// that closely follows the hierarchy of Scala reflection concepts
// for example, a ClassMirror has a companion ModuleMirror and vice versa
val moduleMirror = classMirror.companion.get
// finally, we've arrived at our destination
moduleMirror.instance.asInstanceOf[MetaBase]
}
}
trait MetaBase {
// stuff
}
// ---
class Foo extends Base
object Foo extends MetaBase
object Test extends App {
assert(new Foo().companion == Foo)
}
Actualizar. También vea la excelente publicación de Daniel Sobral: http://dcsobral.blogspot.ch/2012/07/json-serialization-with-reflection-in.html.
Creo que puedes salirte con algo como esto http://stackoverflow.com/questions/1913092/getting-object-instance-by-string-name-in-scala – Noah
Estaba esperando algo bit clean, usando la nueva API de reflexión. – leedm777