Isolate domain models from transaction management. version 2

gistfile1.scala

// dummy session classes for sample codes
final class AnormSession {
  def anormMethod = {
    println("anorm")
  }

  def start = {}
  def commit = {}
}

final class SlickSession {
  def slickMethod = {
    println("slick")
  }

  def start = {}
  def commit = {}
}

// domain layer
trait Entity
trait Repo

case class Context[T](session: T)

case class User(id: Int, name: String) extends Entity

trait UserRepo[T] extends Repo {
  def find(id: Int)(implicit ctx: Context[T]): User
  def store(name: String)(implicit ctx: Context[T]): User
}

// infra layer for persistence
class SlickUserRepo extends UserRepo[SlickSession] {
  def find(id: Int)(implicit ctx: Context[SlickSession]): User = {
    ctx.session.slickMethod // 
    User(2, "slick")
  }

  def store(name: String)(implicit ctx: Context[SlickSession]): User = {
    ctx.session.slickMethod
    User(2, name)
  }
}

class AnormUserRepo extends UserRepo[AnormSession] {
  def find(id: Int)(implicit ctx: Context[AnormSession]): User = {
    ctx.session.anormMethod
    User(2, "slick")
  }
  def store(name: String)(implicit ctx: Context[AnormSession]): User = {
    ctx.session.anormMethod
    User(2, name)
  }
}

// app layer
object App {
  def doSomethingWithSlick() = {
    val session = new SlickSession
    implicit val context = Context(session)

    val repo = new SlickUserRepo
    repo.find(1)
  }

  def doSomethingWithAnorm() = {
    val session = new AnormSession
    implicit val context = Context(session)

    val repo = new AnormUserRepo
    repo.find(2)
  }

  // compile error
  def doSomethingButError() = {
    case class HogeSession()
    val session = new HogeSession
    implicit val context = Context(session)

    val repo = new SlickUserRepo
    repo.find(3)
  }
}