Play Framework Controller 处理多个 Futures

Question

我有一个 Play 控制器，它接收来自用户界面的模型对象。这个模型对象是我要插入数据库的用户。但在我将此用户插入 table 之前，我会检查给定的电子邮件地址是否已经存在重复的用户。如果是，我拒绝请求，如果不是，我插入。我正在使用 Slick and Play 框架，这是我的控制器代码：

  def registerNewUser(user: User) = {
    dbService.registerNewUser(User.toUserRow(user))
      .map(userID => Ok(Json.obj("status" -> "ok", "userId" -> userID)))
      .recover { case ex => InternalServerError(Json.obj("error" -> s"${ex.getMessage}")) }
  }

  def createUser() = Action.async(parse.tolerantJson) { request =>
    request.body.validate[User].fold(
      errors => Future.successful {
        BadRequest(Json.obj("status" -> "error", "message" -> JsError.toJson(errors)))
      },
      user => {
        val userExists: Future[Boolean] = dbService.userExists(user.email)
        userExists.map(value => {
          if (value) UnprocessableEntity(Json.obj("status" -> "error", "message" -> s"user with email ${user.email.toString} already exists"))
          else registerNewUser(user)
        }).recover {
          case ex => InternalServerError(Json.obj("error" -> s"${ex.getMessage}"))
        }
      } // compilation failure on this line [[ Line X ]]
    )
  }

我没有发现这种方法有什么问题，但我的编译器不满意。它在 X 行投诉为：

Expression of type Future[Object] does not confirm to the expected type _X

这里的实际问题是什么？

Answer 1

顺便说一句，你不应该在这里使用 flatMap 而不是 map 吗？

userExists.map(value => {
          if (value) UnprocessableEntity(Json.obj("status" -> "error", "message" -> s"user with email ${user.email.toString} already exists"))
          else registerNewUser(user)
        })

registerNewUser returns Future 对吧？

可能是这样的：

        val userExists: Future[Boolean] = dbService.userExists(user.email)
        userExists.flatMap(value => {
          if (value) Future.successful(UnprocessableEntity(Json.obj("status" -> "error", "message" -> s"user with email ${user.email.toString} already exists")))
          else registerNewUser(user)
        }).recover {
          case ex => InternalServerError(Json.obj("error" -> s"${ex.getMessage}"))
        }

?

Play Framework Controller 处理多个 Futures

Play Framework Controller Handling Multiple Futures

scala

playframework

slick