An example of usage implicit parameters of anonymous functions in Scala: Finagle + RactiveMongo

ImplicitConnection.scala

/**
 * All the magic is done by Scala compiler. 
 */
trait ImplicitMongoConnection[A] {
  def withConnection(block: MongoConnection => A)
                    (implicit connection: MongoConnection): A = block(s)
}

/**
 * This might be a separate file with service implementation.
 */ 
object FooService extends Service[Request, Response] 
    with ImplicitMongoConnection[Future[Response]] {

  // we have to explicitly import implicit value into the scope
  // we can do it at 'file' scope level if there's a bunch of services implemented in single file
  import Main._

  def apply(req: Request): Future[Response] = withConnection { implicit connection =>
    // do all the magic here with 'connection'
    // and pack the result into a future
    Future.never
  }
}

/**
 * This might be a separate file with server/service configuration.
 */ 
object Main extends App {
  val driver = new MongoDriver

  // this value will be used in _all_ services 
  implicit val connection = driver.connection(List("localhost"))
  
  // run the Finagle server on 'foo' service
  val foo = FooService
}