rails 4 collection_select多个嵌套属性未正确保存

Question

我是 Rails 新手，在使用 collection_select 保存连接表的嵌套属性时遇到问题。我有模型 post、tag 和 post_tagging。 post_tagging 是一个连接表。

我想为每个帖子设置多个标签，所以我尝试通过 collection_select 使用多选，但是当我保存时，只有 post_id 被插入到数据库中。下面是我的代码和日志。

Post.rb

class Post < ActiveRecord::Base
  has_many :post_taggings, foreign_key: :post_id, dependent: :destroy
  has_many :tags, through: :post_taggings, source: :tag
  accepts_nested_attributes_for :post_taggings, reject_if: :all_blank, allow_destroy: true
end

标签.rb

class Tag < ActiveRecord::Base
  has_many :post_taggings, foreign_key: :tag_id, dependent: :destroy
  has_many :posts, through: :post_taggings, source: :post
end

post_tagging.rb（我在 post_tagging 模型中关闭了 tag_id 和 post_id 的存在验证，以便获得 POST 的日志。）

class PostTagging < ActiveRecord::Base
  belongs_to :post
  belongs_to :tag

  #validates :post_id, presence: true
  #validates :tag_id, presence: true
end

posts_controller.rb（缩写）

class PostsController < ApplicationController
  def new
    @post = Post.new
    @post.post_taggings.build
  end


  def new_post_params
    params.require(:post).permit(:title, post_taggings_attributes: { :tag_id => [] })
  end

  def update_post_params
    params.require(:post).permit(:title, post_taggings_attributes: [ { :tag_id => [] }, 
                                                               :id, :_destroy ])
  end
end

views/post/new.html.erb

<%= form_for(@post) do |f| %>
<%= f.fields_for :post_taggings do | pt | %> 
    <%= pt.label :post_taggings, "Tags" %><br />
    <%= pt.collection_select(:tag_id, Tag.all, :id, :name, {include_hidden: false}, {multiple: true} ) %><br />
<% end %>

HTML

<select id="post_post_taggings_attributes_0_tag_id" multiple="multiple" name="post[post_taggings_attributes][0][tag_id][]">
  <option value="1">1</option>
  <option value="2">2</option>
  <option value="3">3</option>
  <option value="4">4</option>
  <option value="5">5</option>
  <option value="6">6</option>
  <option value="7">7</option>
  <option value="8">8</option>
  <option value="9">9</option>
  <option value="10">10</option>
</select>

当我保存表单时，我得到以下信息：

Started POST "/posts" for 127.0.0.1 at 2014-12-13 04:22:19 -0800
Processing by PostsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"DaeMJb5b4PcLUz2YfQCjYk1r7pzcMd3NOmhYwEExz2U=", "post"=>{"title"=>"The Title", "post_taggings_attributes"=>{"0"=>{"tag_id"=>["1", "2", "6"]}}}, "commit"=>"Create Post"}
  (0.1ms)  begin transaction
  SQL (0.5ms)  INSERT INTO "posts" ("created_at", "title", "updated_at") VALUES (?, ?, ?)  [["created_at", "2014-12-13 12:22:19.789055"], ["title", "The Title"], ["updated_at", "2014-12-13 12:22:19.789055"]]
  SQL (0.4ms)  INSERT INTO "post_taggings" ("created_at", "post_id", "updated_at") VALUES (?, ?, ?)  [["created_at", "2014-12-13 12:22:19.791928"], ["post_id", 16], ["updated_at", "2014-12-13 12:22:19.791928"]]
 (2.2ms)  commit transaction
Redirected to http://localhost:3000/posts/16
Completed 302 Found in 27ms (ActiveRecord: 3.3ms)

由于它不起作用，我知道我做错了什么。我也不相信编辑案例会起作用。

我觉得我很接近，因为如果我更改强参数，它可以与单个选择一起使用

{ :tag_id => [] } 

到

:tag_id

Answer 1

我更喜欢更方便的方式。

 # in your form

 <%= form_for(@post) do |f| %>

##  your other fields
    <%= f.collection_select(:tag_ids, Tag.all, :id, :name, {include_hidden: false}, {multiple: true} ) %><br />
 <% end %>

#in your controller
 def post_params
  params.require(:post).permit([:title, :tag_ids => []])
 end

现在不是两个不同的允许参数列表，而是两者都适用。删除标签不会很复杂。

请在您操作的所需位置替换您允许的参数值。