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Rails 4 collection_select multiple nested attributes that are not stored properly

I'm new to rails, and I'm having trouble saving nested attributes of the join table using collection_select. I have mail, tag and post_tagging. post_tagging - connection table.

I want to set several tags per message, so I tried using multi-select via collection_select, but only post_id is inserted into the database when saving. Below is my code and log.

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

Tag.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 (I disabled the presence check on tag_id and post_id in the post_tagging model so that I can get the POST log.)

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

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

posts_controller.rb (abbreviated)

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

view / record / 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>

When I save the form, I get the following:

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)

, , - . , .

, , select,

{ :tag_id => [] } 


:tag_id
+4
1

.

 # 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

, . .

, .

+6

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