如何从Mongoid中的嵌入式文档中排除字段? [英] How do I exclude fields from an embedded document in Mongoid?

问题描述

我有一个带有嵌入式标签的Post文档.有时我只显示帖子的标题及其标签.在这种情况下，我会在mongoid中使用以下查询:

I have a Post document that has embedded tags. Sometimes I display only the title of a post and its tags. In those cases, I use the following query in mongoid:

Post.only(:title).find(id)

然后我将查询结果作为json发送到客户端.不幸的是，标签的bson ID使json变得比我需要的大得多. 如何从查询中排除"_id"字段?

I then send the results of the query as json to the client. Unfortunately, the tag's bson id makes the json much larger than I need it to be. How do I exclude the "_id" field from the query?

这是我的模特:

class Post
  include Mongoid::Document
  field :title, :type =>  String
  field :body, :type =>  String
  field :tags, :type =>  Array
  embeds_many :tags
end
class Tag
  include Mongoid::Document  
  field :tag, :type =>  String
  field :type, :type =>  String
  embedded_in :post
end

推荐答案

您将需要使用Mongoid的without方法.这样的事情应该可以解决问题:

You'll need to use Mongoid's without method. Something like this should do the trick:

Post.without(:_id, :body, "tags._id")

将仅返回您所有的帖子标题，以及它们的所有嵌入式标签，并且不返回"_id"字段用于帖子"或标签".

Which will return all your post titles only, as well as all their embedded tags and no _id fields for either Posts or Tags.

我还注意到您在Post模型上定义了field :tags, :type => Array-我认为这是多余的.使用embeds_many会自动为您设置该字段.

I noticed also that you have field :tags, :type => Array defined on your Post model - which I believe is redundant. Using embeds_many sets that field up for you automatically.

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