exhibit-b.scala

// kinja-service library
 
class SsoService extends ApiService {
    def authorByToken(token: String): Author = {
        lookupAuthorInDatabase(token)
    }
}
 
class InvitesService extends Service {
    def invite(token: String, invitee: Author, authorResolver: String => Author): Unit = {
        val inviter = authorResolver(token)
        saveInvitationToDatabase(inviter, invitee)
    }
}

case class InviteMessage(token: String, invitee: Author)
 
 
 
// kinja-core application
 
object SsoService extends service.SsoService

object InvitesService extends service.InvitesService

import service.model.InviteMessage
 
class InvitesActor extends Actor {
    
    def receive = {
        case InviteMessage(token, invitee) => 
            val authorResolver = (tk: String) => SsoService.authorByToken(tk)
            InvitesService.invite(token, invitee, authorResolver)
            // these two lines above are equivalent to 
            // InvitesService.invite(token, invitee, SsoService.authorByToken _)
    }
    
}

val invitesActor = akka.actor.ActorSystem("kinja-core").actorOf(Props(classOf[InvitesActor], "invites-actor"))



// kinja-mantle application

import service.model.InviteMessage

object InvitesApiClient {
    def invite(token: String, invitee: Author): Unit = {
        val invitesService = context.actorSelection("akka.tcp://kinja-core@localhost:2552/user/invites-actor")
        invitesService ! InviteMessage(token, invitee)
    }
}