rails 中的嵌套表单通过 table 多对多关系，不保存属性

Question

我有一个博客模型和一个标签模型，它们通过 table（模型：BlogTag）blog_tags 具有多对多关联。我在博客中实现了一个嵌套表单来为它们添加标签。

我在参数中得到 tags_attributes。但是当我保存博客对象时，它确实将标签对象保存到它，但它确实按 name = nil.

保存了它

Blog model

class Blog < ActiveRecord::Base

  extend FriendlyId
  friendly_id :slugurl, use: :slugged, slug_column: :slugurl

  has_many :blog_tags, dependent: :destroy
  has_many :tags, through: :blog_tags

  accepts_nested_attributes_for :tags

  def self.search(search)
    words = search.to_s.downcase.strip.split.uniq
    words.map! { |word| "tag ~* '\y#{word}\y'" }
    psql = words.join(" OR ")
    self.where(psql)
  end
end

Tag model

class Tag < ActiveRecord::Base
  has_many :blog_tags, dependent: :destroy
  has_many :blogs, through: :blog_tags
end

BlogTag model

class BlogTag < ActiveRecord::Base
  belongs_to :blog
  belongs_to :tag
end

blog_controller

  def new
    @blog = Blog.new
    @blog.tags.build
  end

  def create
    @blog = Blog.new(blog_params)
    save_tag_for
    byebug
    respond_to do |format|
      if @blog.save
        format.html { redirect_to blogs_path, notice: 'Blog was successfully created.' }
        format.json { render :index, status: :created, location: @blog}
      else
        format.html { render :new }
        format.json { render json: @blog.errors, status: :unprocessable_entity }
      end
    end
  end

def blog_params
  params.require(:blog).permit(:blog,
                               :title,
                               :slugurl,
                               tags_attributes: [:name]
  )
end

下面可以看到，在table标签的insert命令中，name字段没有取值，因此变为nil。

Server logs

  (1.2ms)  BEGIN
  SQL (0.9ms)  INSERT INTO "blogs" ("blog", "title", "slugurl", "created_at", "updated_at") VALUES (, , , , ) RETURNING "id"  [["blog", "<p>adsfadsfdfas</p>\r\n"], ["title", "test 11"], ["slugurl", "asdfdf"], ["created_at", "2017-07-19 08:31:32.677338"], ["updated_at", "2017-07-19 08:31:32.677338"]]
  SQL (0.6ms)  INSERT INTO "tags" ("created_at", "updated_at") VALUES (, ) RETURNING "id"  [["created_at", "2017-07-19 08:31:32.684302"], ["updated_at", "2017-07-19 08:31:32.684302"]]
  SQL (1.1ms)  INSERT INTO "blog_tags" ("blog_id", "tag_id", "created_at", "updated_at") VALUES (, , , ) RETURNING "id"  [["blog_id", 20], ["tag_id", 18], ["created_at", "2017-07-19 08:31:32.706957"], ["updated_at", "2017-07-19 08:31:32.706957"]]
   (8.3ms)  COMMIT
Redirected to http://localhost:3000/blogs
Completed 302 Found in 33792ms (ActiveRecord: 15.8ms)

Params

{"utf8"=>"✓", "authenticity_token"=>"+1ZLYPJkQCVOkOSt6dmy9z12XgOMP+OYu0XOOzKUlv+xldd5fkB2RR/oA7qpn53YE+82FDjVeO2ylHkPIEWfVw==", "blog"=>{"title"=>"Programming Languages", "tags_attributes"=>{"0"=>{"name"=>["Python", "C#", ".NET"]}}, "slugurl"=>"pro-lang", "blog"=>"<p>asdfasdfasdf afaadf</p>\r\n"}, "commit"=>"Submit", "controller"=>"blogs", "action"=>"create"}

Form (view)

<%= form_for(@blog) do |f| %>
  <% if @blog.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@blog.errors.count, "error") %> prohibited this blog from being saved:</h2>

      <ul>
      <% @blog.errors.full_messages.each do |message| %>
        <li><%= message %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

          <div class="row">
            <div class="form-group">
            <%= f.label :title ,class: 'control-label' %><br>
            <%= f.text_field :title ,class: 'form-control' %>

            <div class="help-block with-errors"></div>
            </div>
          </div>

          <div class="row">
            <div class="form-group">
              <%= f.fields_for :tags do |tag_builder| %>
                  <%= tag_builder.label :name, "Tag", class: 'control-label' %><br>
                  <%= tag_builder.select :name, Tag.all.pluck(:name,:name), {}, {multiple: true, class: "selectize" } %>
              <%end%>
              <%#= form.select :category_id, Category.all.pluck(:name,:id), {}, {multiple: true, class: "selectize"} %>
              <div class="help-block with-errors"></div>
            </div>
              </div>
          <div class="row">
            <div class="form-group">
            <%= f.label :slugurl ,class: 'control-label' %><br>
            <%= f.text_field :slugurl ,class: 'form-control' %>

            <div class="help-block with-errors"></div>
            </div>
          </div>


          <div class="row">
            <div class='form-group'>
             <%= f.label :blog ,class:'control-label'%><br>
             <%= f.cktext_area :blog, rows: 10,class:'form-control' %>
            <div class="help-block with-errors"></div>
            </div>
          </div>

              <div class="form-actions mg-t-lg">
                <div class="row">
                  <div class="col-sm-7 col-sm-offset-5">
                    <div class="text-center-xs">
                      <input type="submit" name="commit" value="Submit" class="btn btn-contrast" />
                    </div>
                    </div>
                </div>
                </div>

<% end %>

Answer 1

I am getting tags_attributes in params. But when I save the blog object it does save the tag object to it but it does save it by name = nil.

根据 params 散列，您要为 name 发送多个值，因此您需要修改 blog_params 以接受 name 的多个值。

def blog_params
  params.require(:blog).permit(:blog,
                               :title,
                               :slugurl,
                               tags_attributes: [name: []]
  )
end

rails 中的嵌套表单通过 table 多对多关系，不保存属性

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