Simple Dependency Injector

gistfile1.scala

/////////////////////////
// Dependency Injector //
/////////////////////////

import scala.collection.immutable.HashMap

object Injector {
  private var registry = new HashMap[java.lang.Class[_], Any]

  def inject[T : Manifest] : T = {
    val from = manifest[T].erasure
    registry.get(from).asInstanceOf[Option[T]] match {
      case Some(o) => o
      case None => throw new RuntimeException("Unable to inject %s: no implementation bound".format(from))
    }
  }

  def bind[T : Manifest](to: AnyRef) : Unit = {
    val from = manifest[T].erasure
    registry += from -> to
  }
}

//////////////////
// Sample usage //
//////////////////

import Injector._

trait UserService {
  def create : String
}

class DefaultUserService extends UserService {
  override def create = "Alois Cochard"
}

class Collaborator {
  private lazy val userService = inject[UserService]

  def start() {
    println(userService.create)
  }
}

bind[UserService](new DefaultUserService)
new Collaborator().start

bind[List[String]](List("hello", "dependecy", "injection", "world"))
println(inject[List[String]].mkString(" "))