Justin's example refactored for currying ..

gistfile1.scala

// like to keep domain objects pure
// hence moved repository injection to the service module

case class User(name: String)

trait UserRepository{
  def save(user: User): Unit
}

class RiakUserRepository extends UserRepository{
  def save(user: User) = println("saves to Riak")
}

class MongoUserRepository extends UserRepository{
  def save(user: User) = println("saves to Mongo")
}

object UserService {
  val create: UserRepository => String => Unit = {repo => name => repo.save(User(name))}
}

object RiakContext {
  import UserService._
  val create_c = create(new RiakUserRepository) // returns a fn (String) => Unit
}

object MongoContext {
  import UserService._
  val create_c = create(new MongoUserRepository) // returns a fn (String) => Unit
}

object Main_1 {
  def run_1 = {
    import RiakContext._
    create_c("justin")
  }

  def run_2 = {
    import MongoContext._
    create_c("justin")
  }
}

Please, could you explain why you chose "createForRiak" to be a def and not a val?

should be a val .. changed ..

This can be done with the above design as well .. I have updated the gist above .. Please review ..