It is correcto to instantiate val in scala trait?

Question

I'm working in a spray, akka, scala, reactivemongo project and I have this trait

trait PersistenceManager {

  val driver = new MongoDriver
  val connection = driver.connection(List("localhost"))

  def loan[A](collectionName: String)(f: BSONCollection => Future[A]): Future[A] = {
    val db = connection("flujo_caja_db")
    val collection = db.collection(collectionName)
    f(collection)
  }
}

Also I have Dao's objects to use that trait like so:

object Dao extends PersistenceManager {

   def find = loan("users"){
     collection =>
          collection.find(BsonDocument())....
   }

}

It is correct to instanciate those database vals in my persistencemanager trait? It works really good.

Thank you!

Answer 1

I'm thinking you want things defined like this, to prevent multiple MongoDriver and connection pools from being created:

object PersistenceManager{
  val driver = new MongoDriver
  val connection = driver.connection(List("localhost"))
}


trait PersistenceManager {
  import PersistenceManager._

  def loan[A](collectionName: String)(f: BSONCollection => Future[A]): Future[A] = {
    val db = connection("flujo_caja_db")
    val collection = db.collection(collectionName)
    f(collection)
  }
}