如何在has_scope中使用actions -as- tagable -on

Question

我正在构建一个API，返回一个帖子列表(localhost:3000/API/v1/posts):

{
  "tags": [
    {
      "id": 1,
      "name": "Tag 1"
    },
    {
      "id": 2,
      "name": "Tag 2"
    },
    …
  ],
  "posts": [
    {
      "id": 1,
      "title": "Post 1",
      "body": "Lorem ipsum dolor sit amet.",
      "tag_ids": [
        1
      ]
    },
    {
      "id": 2,
      "title": "Post 2",
      "body": "Lorem ipsum dolor sit amet.",
      "tag_ids": [
        2
      ]
    },
    …
  ]
}

这些帖子使用acts-as- tagable -on gem标记。我想能够过滤他们基于这些标签使用has_scope gem (localhost:3000/api/v1/posts?tag_id=1):

{
  "tags": [
    {
      "id": 1,
      "name": "Tag 1"
    }
  ],
  "posts": [
    {
      "id": 1,
      "title": "Post 1",
      "body": "Lorem ipsum dolor sit amet.",
      "tag_ids": [
        1
      ]
    }
  ]
}

但是我不知道如何在我的模型中设置by_tag_id作用域，因为acts-as- tagable -on文档只解释了如何根据它们的标记名称(使用tagged_with()方法)找到对象。

提前感谢您的帮助!: -)

大卫

Answer 1

对于那些感兴趣的，我解决了这样的问题，这是我的Post模型:

class Post < ActiveRecord::Base
  attr_accessible :title, :body, :tag_list
  # Alias for acts_as_taggable_on :tags
  acts_as_taggable
  # Named scope which returns posts whose tags have a specific ID
  scope :tagged_with_id, lambda { |tag_id| joins(:taggings).where(:taggings => {:tag_id => tag_id}) }
end

和我的Posts控制器:

class PostsController < ApplicationController
  has_scope :tagged_with_id
  def index
    @posts = apply_scopes(Post).all
    render :json => @posts
  end
end