使用reactmongo在mongodb上进行计数查询时出错

debugcn 发表于 Dev

阿尔贝托·阿达米

我正在编写一个play 2.3.2应用程序。在我的应用程序中，我使用MongoDB数据库。我有一个requestion.tags和recommendation.request集合。它们具有以下JSON格式：1）Recommendation.tags：

 {
    "_id" : ObjectId("542e65fb7ab45a4189944137"),
    "tag" : "Meat:Pork - Bacon Cooked Slcd"
}

2）Recommendation.requests

{
    "_id" : ObjectId("542e67e07f724fc2af28ba74"),
    "id" : "6649fd2b-c616-4693-aec5-a2a2a1658417",
    "user" : {
        "id" : "",
        "email" : "[email protected]"
    },
    "tags" : [
        {
            "tag" : "Fish:Swordfish Loin Portions"
        },
        {
            "tag" : "Vegetable:Carrots - Jumbo"
        }
    ],
    "date" : 1412327392380
}

我正在编写一个处理所有统计信息请求的控制器。在这种情况下，我正在编写一种搜索系统中最常用标签的方法。为此，我将反应式mongo驱动程序用于scala。这是使用的代码：

/**
   * Method that search the most used tag.
   */
  def max = Action {
   var max = 0
   var tag = null
   val tags: Future[List[Tag]] = Tags.find(Json.obj()).toList
   for{
     tag <- tags
     tagsOk <- Requests.find(Json.obj("tags.tag" -> tag.category + " " + tag.name)).count
     if(tagsOk > max) {
       max = tagsOk
       tag = tag.category + " " + tag.name //string tag
     }
   }
   Ok(tag)
 }

但是编译器给我以下错误：

[error] /Users/alberto/git/bdrim/modules/recommendation-system/app/recommendationsystem/controllers/manager/StatisticsController.scala:28: identifier expected but string literal found.
[error]      tagsOk <- Requests.find(Json.obj("tag" : tag.category + " " + tag.name)).count
[error]                                                              ^
[error] /Users/alberto/git/bdrim/modules/recommendation-system/app/recommendationsystem/controllers/manager/StatisticsController.scala:33: ')' expected but '}' found.
[error]    }
[error]    ^
[error] two errors found
[error] (compile:compile) Compilation failed

怎么了？？

@编辑

[error] /Users/alberto/git/bdrim/modules/recommendation-system/app/recommendationsystem/controllers/manager/StatisticsController.scala:28: value category is not a member of List[recommendationsystem.models.Tag]
[error]          tagsOk <- Requests.find(Json.obj("tags.tag" -> tag.category + " " + tag.name)).count
[error]

@newedit

我已经解决了使用以下代码：

val tags = for{
         tags <- futureTags
       }
       for(document <- tags) {
         val tagsOk = Requests.find(Json.obj("tags.tag" -> document.category))

       }

有没有一种方法可以获取List [T]并对其进行相同的迭代？

阿尔贝托·阿达米

解决使用

def max = Action {
   var max: Int = 0
   var tagFound: Tag = null
   //obtain all the tags in the db.
   val futureTags: Future[List[Tag]] = Tags.all.toList
   futureTags map{ (tags: List[Tag]) => 
                        tags map {
                          (tag: Tag) => 
                            //create the tag String 
                            val tagName = tag.category  + ":" + tag.attr 
                            //search the documents where tags.tag == tag in the db.
                            val futureRequests : Future[List[recommendationsystem.models.Request]]= Requests.find(Json.obj("tags.tag" -> tagName)).toList
                            futureRequests map { (requests: List[recommendationsystem.models.Request]) =>
                                                    //get the numbers of documents matching the tag
                                                    val number = requests.size
                                                    if(number > max) {
                                                      max = number
                                                      tagFound = tag
                                                    }

                            }

                        }
    }