在 Rails 4 论坛应用程序中创建嵌套模型

Question

您好，我在Rails 4 中做一个论坛应用。它可以有很多论坛，每个论坛都有很多主题。每个主题可以有很多 post。创建新主题时，还必须创建初始 post，就像 Stack Overflow 本身一样。因此，我有一个 "New Topic" 形式的文本区域，允许使用 fields_for 方法。 问题是，当您在填写表格（包括"post"字段）后单击"Create Topic"按钮时，事务被回滚。出现以下验证错误：

3 errors prohibited this topic from being saved:

Posts forum must exist

Posts topic must exist

Posts user must exist

这是我的表格：app/views/topics/_form.html.erb

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

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

  <div class="field">
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </div>

  <div class="field">
    <%= f.fields_for :posts do |builder| %>
      <%= builder.label :content %><br>
      <%= builder.cktext_area :content, class: 'ckeditor' %>
    <% end %>
  </div>

  <div class="actions">   
    <%= f.submit 'Create Topic', class: "btn btn-l btn-success" %>
  </div>
<% end %>

型号：forum.rb

class Forum < ApplicationRecord
    has_many :topics, dependent: :destroy
    has_many :posts, through: :topics

    def most_recent_post
      topic = Topic.last
      return topic
    end
end

topic.rb

class Topic < ApplicationRecord
  belongs_to :forum
  belongs_to :user

  has_many :posts, dependent: :destroy
  accepts_nested_attributes_for :posts

end

post.rb

class Post < ApplicationRecord
  belongs_to :forum
  belongs_to :topic
  belongs_to :user

  validates :content, presence: true
end

主题控制器，app/controllers/topics_controller.rb

class TopicsController < ApplicationController
  before_action :get_forum
  before_action :set_topic, only: [:show, :edit, :update, :destroy]

  # GET /topics
  # GET /topics.json
  def index
    @topics = @forum.topics
  end

  # GET /topics/1
  # GET /topics/1.json
  def show
  end

  # GET /topics/new
  def new
    @topic = @forum.topics.build
    @topic.posts.build
  end

  # GET /topics/1/edit
  def edit
    # @topic.posts.build
  end

  # POST /topics
  # POST /topics.json
  def create
    @topic = @forum.topics.build(topic_params.merge(user_id: current_user.id))
    @topic.last_poster_id = @topic.user_id

    respond_to do |format|
      if @topic.save
        format.html { redirect_to forum_topic_path(@forum, @topic), notice: 'Topic was successfully created.' }
        format.json { render :show, status: :created, location: @topic }
      else
        format.html { render :new }
        format.json { render json: @topic.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /topics/1
  # PATCH/PUT /topics/1.json
  def update
    respond_to do |format|
      if @topic.update(topic_params)
        format.html { redirect_to forum_topic_path(@forum, @topic), notice: 'Topic was successfully updated.' }
        format.json { render :show, status: :ok, location: @topic }
      else
        format.html { render :edit }
        format.json { render json: @topic.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /topics/1
  # DELETE /topics/1.json
  def destroy
    @topic.destroy
    respond_to do |format|
      format.html { redirect_to forum_path(@forum), notice: 'Topic was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def get_forum
      @forum = Forum.find(params[:forum_id])
    end

    def set_topic
      @topic = Topic.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def topic_params
      params.require(:topic).permit(:title, :last_poster_id, :last_post_at, :tags, :forum_id, :user_id, posts_attributes: [:id, :content])
    end
end

如您所见，我已将 posts_attributes 添加到 topic 的强参数中。这些是 posts 除了外键引用 (:forum_id, :topic_id, :user_id) 之外仅有的字段。我试过将这些属性放入，但我得到了同样的错误。

最后，这是我的routes.rb

Rails.application.routes.draw do

  resources :forums do
    resources :topics do
      resources :posts
    end
  end
  resources :sessions
  resources :users
  mount Ckeditor::Engine => '/ckeditor'
end

我还应该提到，我已经尝试在 fields_for 中添加 hidden_fields，并使用 @forum、@topic 和 current_user 的 id 标准。这会引发相同的验证错误。

我错过了什么？我觉得这是控制器中的东西。就像我没有正确保存它一样。我见过的每个教程都是这样的。除了 Rails <=3 版本，它们因没有 strong_params 而有很大不同。

有什么想法吗？感谢您的帮助！

EDIT 这是我尝试提交标题为 "I am a title" 且内容为 "I am some content"...

的日志输出

Started POST "/forums/1/topics" for 127.0.0.1 at 2016-01-31 09:03:33 -0500
Processing by TopicsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"pYt842XQHiOKqNjPHBO8lNP2z92gHF7Lpt24CppbuvHR/cFHky3FVCpBs77p7WFRKmYBHgeZQjx0sE+DI+Q+sQ==", "topic"=>{"title"=>"I am a title", "posts_attributes"=>{"0"=>{"content"=>"<p>I am some content</p>\r\n"}}}, "commit"=>"Create Topic", "forum_id"=>"1"}
  Forum Load (0.6ms)  SELECT  "forums".* FROM "forums" WHERE "forums"."id" =  LIMIT   [["id", 1], ["LIMIT", 1]]
  User Load (0.6ms)  SELECT  "users".* FROM "users" WHERE "users"."id" =  LIMIT   [["id", 1], ["LIMIT", 1]]
   (0.3ms)  BEGIN
  CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" =  LIMIT   [["id", 1], ["LIMIT", 1]]
   (0.4ms)  ROLLBACK

Answer 1

这不是一个直接的答案；评论太长了。

您 routes 的一个问题是您 nesting too many resources:

Resources should never be nested more than 1 level deep...
resources :x do
  resources :y
end

--

尽管您可以做您正在做的事情，但使用 scope:

可能会更好

#config/routes.rb
scope ':forum' do
   resources :topics do
      resources :posts
   end
end

您面临的问题是事情会变得非常复杂、非常迅速。虽然

通过这种方式，您可以使 forums CRUD 在其自己的一组功能中可访问：

#config/routes.rb
resources :forums #-> only accessible to admins?
scope ...

无论哪种方式，您仍然需要使用存在的 forum 来定义您的路线：

<%= link_to "Test", [@forum, @topic, @post] %>

在 Rails 4 论坛应用程序中创建嵌套模型

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