(提升)在CSS选择器转换过程中对项目进行分组? [英] (Lift) Grouping items during CSS selector transform?

问题描述

希望获得一些指导.

请考虑以下代码段:

val q = (for {
    (d, o) <- dx innerJoin ox on (_.user === _.id)
   } yield(d,o))

  "div" #>  q.map { case (x, y) =>
  {
       ".dF1 *" #> x.name &
       ".dF2 *" #> y.id
  }
}

在此查询中，我有两个表，其中"ox"表是人员列表，"dx"是与这些人员关联的项目的列表. 就本文而言，它很好用，但是我最终为一个人拥有的每一项创建一行.因此，假设有三个用户，前两个有两个项目，最后一个有1，我得到五行:

in this query, I have two tables, where table "ox" is a list of people, and "dx" is a list of items associated with those people. As it is written, it works good, but I end up creating one row for each item that a person has. So assume three users, first two have two items, and last one has 1, i get five rows:

<div class="dF1">[user1]</div><div class="dF2">[item1]</div>
<div class="dF1">[user1]</div><div class="dF2">[item2]</div>
<div class="dF1">[user2]</div><div class="dF2">[item1]</div>
<div class="dF1">[user2[</div><div class="dF2">[item2]</div>
<div class="dF1">[user3]</div><div class="dF2">[item3]</div>

我想做的是为每个用户创建一行，然后在dF2字段内创建多个div，每个项一个.布局将是:

What I'd like to do is create a single row for each user, and inside of the dF2 field create multiple divs, one for each item. The layout would then be:

<div class="dF1">[user1]</div><div class="dF2">[item1] [item2]</div>
<div class="dF1">[user2]</div><div class="dF2">[item1] [item2]</div>
<div class="dF1">[user3]</div><div class="dF2">[item1]</div>

我该怎么做?我需要使用中介馆藏吗?

How can I do this? Do I need to use an intermediary collection?

推荐答案

此处有两个选项，您可以使用数据库返回按字段分组的集合，也可以使用Scala对集合进行分组.如果使用数据库，则只能按字段分组，例如x.name，但是执行效率可能更高.如果与Scala进行分组，则可以按整个对象x进行分组，但是最终将需要进行更多的处理和对象创建.您需要确定最适合您的.

You have two options here, you can either use the database to return a collection grouped by a field or you can use Scala to group your collection. If you use the database, you will be limited to grouping by a field, like x.name, but your execution will likely be more efficient. If you group with Scala you'll be able to group by the entire object x, but you will end up doing more processing and object creation. You'd need to decide which is best for you.

现在，这样说-假设我们正在使用Scala.您将执行以下操作:

Now, that said - let's assume we're using Scala. You would do something like this:

"div" #>  q.groupBy(_._1).map { case (x, y) =>
  {
       ".dF1 *" #> x.name &
       ".dF2 *" #> y.map{ case (x2, y2) => y2.id}.mkString(" ") 
  }
}

groupBy不会直接使用查询中包含D和O的List，而是会创建一个类型为Map[D, List[(D, O)]]的列表.在上面的示例中，我只是将o的id字段组合为一个字符串以输出，就像您请求的示例一样.

Instead of working directly with the List containing D and O from your query, the groupBy will create a list of type: Map[D, List[(D, O)]]. In the example above, I am just combining the id field of your o into a single string to output which looked like the example you requested.

除了单个字符串，您还可以让第二个映射返回CssSel进行进一步的转换.此示例将查找嵌套在具有类dF2的div中的<div class="dF2SubDiv"></div>:

Instead of a single string, you could also have your second map return a CssSel to do further transformations. This example which will look for <div class="dF2SubDiv"></div> nested in the div that has the class dF2:

"div" #>  q.groupBy(_._1).map { case (x, y) =>
  {
       ".dF1 *" #> x.name &
       ".dF2" #> y.map{ case (x2, y2) => 
           ".dF2SubDiv *" #>  y2.id
        }
  }
}

如果您更愿意使用Slick来进行分组，则可以在这里.

If you would rather use Slick to do the groupBy, you could find more info on it here and here.

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