scala - 如何将()注入(inject)到具有构造函数参数的类中？

Question

我有一个 WebSocket创建每个连接参与者处理程序的 Controller :

class WebSocketController @Inject()(cc: ControllerComponents)(implicit exc: ExecutionContext) {
  def socket: WebSocket = WebSocket.accept[JsValue, JsValue] { request =>
    ActorFlow.actorRef { out => // Flow that is handled by an actor from 'out' ref
      WebSocketActor.props(out) // Create an actor for new connected WebSocket
    }
  }
}

在 Actor 处理程序中，我需要使用 ReactiveMongo :

trait ModelDAO extends MongoController with ReactiveMongoComponents { 
  val collectionName: String
  ...
}
class UsersCollection @Inject()(val cc: ControllerComponents,
                                val reactiveMongoApi: ReactiveMongoApi,
                                val executionContext: ExecutionContext,
                                val materializer: Materializer)
  extends AbstractController(cc) with ModelDAO {
  val collectionName: String = "users"
}

所以，通常的方法是 @Inject() UsersCollection在目标类中。但我不能做这样的事情:

class WebSocketActor @Inject()(out: ActorRef, users: UsersCollection) extends Actor { ... }

因为actor实例在 WebSocketActor内部创建伴生对象:

object WebSocketActor {
  def props(out: ActorRef) = Props(new WebSocketActor(out))
}

如何使用 UsersCollection里面 WebSocketActor ?

Answer 1

您可以创建 Actor 谁的依赖项将由 Play 自动注入(inject)。没问题。 (https://www.playframework.com/documentation/2.6.x/ScalaAkka)

但是如果是网络套接字， Prop 预期的 Actor ，但不是 Actor (或 ActorRef)本身。

ActorFlow.actorRef { out => // Flow that is handled by an actor from 'out' ref
   WebSocketActor.props(out) // <- ACTOR IS NOT CREATED HERE, WE RETURN PROPS
}

所以在这种情况下没有办法自动完成(至少我没有找到它)。

你可以做的是通过 UsersCollection手动。

class WebSocketController @Inject()(cc: ControllerComponents, usersCollection: UsersCollection)(implicit exc: ExecutionContext) {
  def socket: WebSocket = WebSocket.accept[JsValue, JsValue] { request =>
    ActorFlow.actorRef { out => // Flow that is handled by an actor from 'out' ref
      WebSocketActor.props(out, usersCollection) //<- ACTOR IS NOT CREATED HERE, WE RETURN PROPS
    }
  }
}

注意到我注入(inject)了 UsersCollection进入 WebSocketController并将其传递给 Prop 。

简单，我没有看到任何缺点。