Reactivemongo 和 Play，链接查询

Question

Scala（最新）、Reactivemongo（最新）和 Play 框架 (2.3.x) 有点新。

验证会话，并在成功时加载用户对象并将其返回为 json。我猜问题是特定于映射和期货的。以下代码无法编译：

def userCheck(token: String) = Action.async {
  val futureSession = sessionCollection.find(Json.obj("token" -> token)).one[BSONDocument]

  futureSession.map {
    case Some(session) => {
      userCollection.find(Json.obj("_id" -> session.getAs[String]("userId").get )).one[JsObject].map {
        case Some(user) => Ok(JsObject(Seq("user" -> user)))
        case None => NotFound( JsObject(Seq("message" -> JsString("not found"))) )
      }
    }
    // NotFound( JsObject(Seq("message" -> JsString("not found"))) )
    case None => NotFound( JsObject(Seq("message" -> JsString("not found"))) )
  }
}

所以，错误信息是：

[error] AuthController.scala:186: overloaded method value async with alternatives:
[error]   [A](bodyParser: play.api.mvc.BodyParser[A])(block: play.api.mvc.Request[A] => scala.concurrent.Future[play.api.mvc.Result])play.api.mvc.Action[A] <and>
[error]   (block: play.api.mvc.Request[play.api.mvc.AnyContent] => scala.concurrent.Future[play.api.mvc.Result])play.api.mvc.Action[play.api.mvc.AnyContent] <and>
[error]   (block: => scala.concurrent.Future[play.api.mvc.Result])play.api.mvc.Action[play.api.mvc.AnyContent]
[error]  cannot be applied to (scala.concurrent.Future[Object])
[error]   def userCheck(token: String) = Action.async {

如果您查看源代码，您会看到注释行，如果我取消注释，代码将编译。我是否遗漏了一些案例？

更新 1：

因此，根据已接受答案中的提示，我想出了这个：

def userCheck(token: String) = Action.async {
  getSession(token).flatMap {
    session => {
      session match {
        case Some(s) => {
          getUser( s.getAs[String]("userId").get ).flatMap {
            user => {
              user match {
                case Some(u) => Future.successful( Ok( u ) )
                case None => Future.successful( NotFound( JsObject(Seq( "m" -> JsString("User not found")))))
              }
            }
          }
        }
        case None => Future.successful( NotFound( JsObject(Seq( "m" -> JsString("Session not found")))))
      }
    }
  }
}

def getSession(token: String): Future[Option[BSONDocument]] = {
  sessionCollection.find( Json.obj("token" -> token) ).one[BSONDocument]
}

def getUser(id: String): Future[Option[JsObject]] = {
  userCollection.find( BSONDocument( "_id" -> BSONObjectID(id) ) ).one[JsObject]
}

...它成功了。不过感觉需要重构。

Answer 1

尝试向所有分支添加显式类型；特别是，确保 case Some(Session) return 之后的块是 Result 或您认为应该是的任何内容。我怀疑在 Some 分支中你得到的是 Future[Future[Result]] 而不是 Future[Result] - 也许你需要做 futureSession.flatMap，而在 None案例 return Future.successful(...).

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