scalaにおけるimplicitによる依存注入

import scala.collection.mutable


/**
 * Created by xiaojun on 2015/2/17.
 */
object ScalaDemo extends App {


  case class User(userId: Int, userName: String)

  class UserDao {
    var users = mutable.HashMap((1, User(1, "aaa")), (2, User(2, "bbb")), (3, User(3, "ccc")))

    def findById(userId: Int) = users.get(userId)

    def findAll() = users

    def updateById(u: User) = users.update(u.userId, u)

  }

  implicit val userDao = new UserDao


  class UserService(implicit dao: UserDao) {
    def getAllUsers() = dao.findAll()

    def updateUser(u: User) = dao.updateById(u)
  }
  //           UserDao   ,         userDao   UserService   
  val service = new UserService

  println(service.getAllUsers())

  //  users userid=1   
  service.updateUser(User(1, "AAA"))
  println(service.getAllUsers())

  //    UserService  service2,        service   users      ,          userDao  
  val service2 = new UserService
  println(service2.getAllUsers())

}