在我的Play2应用程序中使用Future进行getOrElse时,获取值映射不是Object的成员

Question

当我用ReactiveMongo调用我的mongo实例时,我正在尝试进行理解.该方法应检查是否返回任何结果,如果不返回Future(NotFound).但我收到一个我不明白的错误.

[info] Compiling 8 Scala sources and 1 Java source to /Users/Projects/reco_play/parser/target/scala-2.10/classes...
[error] /Users/Projects/reco_play/parser/app/controllers/Application.scala:94: value map is not a member of Object
[error]           }.getOrElse(Future(NotFound))
[error]                      ^
[error] one error found
[error] (compile:compile) Compilation failed

进口:

import play.api.mvc._
import play.api.Play.current
import play.api.Logger
import play.modules.reactivemongo.{ReactiveMongoPlugin, MongoController}
import models.{Company}
import reactivemongo.api.collections.default.BSONCollection
import reactivemongo.bson.{BSONObjectID, BSONDocument}
import org.joda.time.DateTime
import scala.concurrent.{Future, ExecutionContext}

方法:

def showEditForm(id: String) = Action {
    implicit request =>
      implicit val reader = Company.CompanyReader
      Async {
        val objectId = new BSONObjectID(id)
        val cursor = collection.find(BSONDocument("_id" -> objectId)).cursor[Company]

        for {
          maybeCompany <- cursor.headOption
          result <- maybeCompany.map { company =>
              Ok(views.html.editForm(Some(id), Company.form.fill(company)))
          }.getOrElse(Future(NotFound))
        } yield result
      }
  }

Answer 1

好的,我更多地看了你的例子,你是对的,这是一个与我最初回答的问题不同的问题.首先,尝试将for-comp更改为:

    for {
      maybeCompany <- cursor.headOption
    } yield {
       maybeCompany.map{company => 
        Ok(views.html.editForm(Some(id), Company.form.fill(company)))
      }.getOrElse(NotFound)
    }

您看到的问题与for-comp中的混合类型有关.您使用a启动了for-comp,Future然后尝试切换到Option下一步.这是for-comps的一个不幸的特征,因为你在第一行开始的任何类型都是你在整个理解过程中必须继续的相同类型.这是因为你不能flatMap从Future[T]到Option[T]这是在你有换补偿会发生什么.另一种方法如下:

    for {
      maybeCompany <- cursor.headOption
      result <- Promise.successful(maybeCompany.map { company =>
          Ok(views.html.editForm(Some(id), Company.form.fill(company)))
      }).future
    } yield result.getOrElse(NotFound)

在这种方法中,在for-comp的第二步,我将Option结果包装成成功完成Future,这是用于继续理解的正确类型.