Rails .build不是在建造has_many：选项

Question

我有一个带有3种型号的民意调查应用程序。

poll.rb

class poll < ApplicationRecord
  validates_presence_of :user, :title
  belongs_to :user
  has_many :questions, dependent: :destroy
  has_many :options, through: :questions

  accepts_nested_attributes_for :questions
end

Question.rb

class Question < ApplicationRecord
  validates_presence_of :poll_id, :question_id, :title
  belongs_to :poll
  has_many :options
  accepts_nested_attributes_for :options, reject_if: proc { |attributes| attributes['title'].blank? }
end

option.rb

class Option < ApplicationRecord
  validates_presence_of :question_id, :title
  belongs_to :question
  belongs_to :poll
end

我希望该问题表格具有添加选项的字段，因此我将其添加到Question _form中。

  <%= form.fields_for :option do |o| %>
    <div>
      <%= o.label "Option", style: "display: block" %>
      <%= o.text_field :title, placeholder: "Enter Option here" %>
    </div>
  <% end %>

我现在可以看到一个很好的选项块。尽管我希望有3个POSSBILE选项，因此在Question_controller.rb中我添加了以下内容：

 def new
    @question = @poll.questions.build
    3.times { @question.options.build } # 3 different options 
  end

尽管如此，我只看到一个选项块而不是3个选项块。为什么是这样，我该如何解决？ 此外，我没有看到“ postgresql”表中的新条目。

---

完整的问题_controller.rb

class QuestionsController < ApplicationController
  before_action :set_question, only: %i[ show edit update destroy ]
  before_action :set_poll

  # GET /questions or /questions.json
  def index
    @questions = Question.all
  end

  # GET /questions/1 or /questions/1.json
  def show
  end

  # GET /questions/new
  def new
    # @question = Question.new
    @question = @poll.questions.build
    3.times { @question.options.build } # 5 different options 
  end
  
  # GET /questions/1/edit
  def edit
  end

  # POST /questions or /questions.json
  def create
    @question = Question.new(question_params)
    

    respond_to do |format|
      if @question.save
        format.html { redirect_to polls_question_url(@question), notice: "Question was successfully created." }
        format.json { render :show, status: :created, location: @question }
      else
        format.html { render :new, status: :unprocessable_entity }
        format.json { render json: @question.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /questions/1 or /questions/1.json
  def update
    respond_to do |format|
      if @question.update(question_params)
        format.html { redirect_to polls_question_url(@question), notice: "Question was successfully updated." }
        format.json { render :show, status: :ok, location: @question }
      else
        format.html { render :edit, status: :unprocessable_entity }
        format.json { render json: @question.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /questions/1 or /questions/1.json
  def destroy
    poll_id = Question.find_by(params[:poll_id])
    session[:return_to] ||= request.referer
    @question.destroy

    respond_to do |format|
      format.html { redirect_to session.delete(:return_to), notice: "Question was successfully destroyed." }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_question
      @question = Question.find(params[:id])
    end

    # Only allow a list of trusted parameters through.
    def question_params
      params.require(:question).permit(:poll_id, :question_type, :title, :description, :randomize_selection, :voter_abstain, { option_attributes: [:question_id, :poll_id, :party_id, :title, :description] } )
    end

    def set_poll
      @poll = poll.find_by(params[:poll_id])
    end

end

路由.rb

  resources :users do
    resources :polls
  end
  resource :polls do
    resources :questions 
  end

  resource :questions do
    resources :options
  end

编辑：

---

这是我的问题部分。

_form.html.erb

<%= form_with(model: [@Poll, question] ) do |form| %>
  <% if question.errors.any? %>
    <div style="color: red">
      <h2><%= pluralize(question.errors.count, "error") %> prohibited this question from being saved:</h2>
      <ul>
        <% question.errors.each do |error| %>
          <li><%= error.full_message %></li>
        <% end %>
      </ul>
    </div>
  <% end %>

  <div>
    <%= form.hidden_field :poll_id %>
  </div>

  <div>
    <%= form.label :question_type, style: "display: block" %>
    <%= form.text_field :question_type %>
  </div>

  <div>
    <%= form.label :title, style: "display: block" %>
    <%= form.text_field :title %>
  </div>

  <div>
    <%= form.label :description, style: "display: block" %>
    <%= form.text_area :description %>
  </div>

  <div>
    <%= form.label :randomize_selection, style: "display: block" %>
    <%= form.check_box :randomize_selection %>
  </div>

  <div>
    <%= form.label :voter_abstain, style: "display: block" %>
    <%= form.check_box :voter_abstain %>
  </div>

  <div>
  <%= form.fields_for :options do |o| %>
    <div>
      <%= o.label "Option", style: "display: block" %>
      <%= o.text_field :title, placeholder: "Enter Option here" %>
    </div>
  <% end %>
  </div>

  <div>
    <%= form.submit %>
  </div>
<% end %>

这是我正在渲染表格的民意调查表演。

show.html.erb

<p style="color: green"><%= notice %></p>

<p>
  <strong>Poll Title:</strong>
  <%= @poll.title %>
  <%= render @poll %>
</p>
<div>
  <%= link_to "Edit this poll", edit_user_poll_path(@poll) %> |
  <%= link_to "Back to polls", user_polls_path %> |
  <%= link_to "Destroy this poll", user_poll_path(@poll), method: :delete %>
</div>

<% if @poll.questions.any? %>
  <hr>
  <h2>Questions:</h2>
  <%= render @poll.questions %>
  
<% end %>
<hr>


<h2>Add a new Question:</h2>
<%= render "questions/form", question: @poll.questions.build %>

Answer 1

您传递给fields_for的参数必须与模型上的关联名称匹配：

<%= form.fields_for :options do |o| %>
  <div>
    <%= o.label "Option", style: "display: block" %>
    <%= o.text_field :title, placeholder: "Enter Option here" %>
  </div>
<% end %>

非常仔细注意Rails中的复数。这是使惯例超过构型为您服务而不是与您不利的重要组成部分。

但是，此代码还有很多其他问题。

• 常数应始终是camelcase或大写 Ruby中的大写 - 您需要将类Poll将更改为class poll并修复全部对班级的引用。这不仅仅是一种风格问题，因为口译员对以大写字母开始完全不同的是标识符。
• 您没有正确嵌套。您有一条嵌套的路线，但是您仍将其视为控制器和docstrings中的非嵌套资源。
• 您正在通过参数白名单中的父级ID。 ：poll_id和：Question_id不应将其列入白色。请勿使用隐藏输入传递父ID。问题ID由Rails分配 - 您不应该信任用户通过它。
• 该选项不需要poll_id。使用间接HAS_ONE关联进行树上。这可能会导致一个问题及其选项属于不同民意调查的边缘情况。

首先让我们修复模型：

class Poll < ApplicationRecord
  # belongs_to assocations are required by default
  # adding validations will just cause duplicate error messages
  validates_presence_of :title
  belongs_to :user
  has_many :questions, dependent: :destroy
  has_many :options, through: :questions
  accepts_nested_attributes_for :questions
end

class Question < ApplicationRecord
  validates_presence_of :title
  belongs_to :poll
  has_many :options
  accepts_nested_attributes_for :options, reject_if: proc { |attributes| attributes['title'].blank? }
end

class Option < ApplicationRecord
  validates_presence_of :title
  belongs_to :question
  has_one :poll, through: :question
end

然后，我建议您使用 shallow nesting

resource :polls do
  resources :questions, shallow: true
end

创建问题成员路由（显示，编辑，删除），而无需/polls/：Poll_ID prefix collection collection路由新的）是嵌套的。

并且您将控制器设置为：

class QuestionsController < ApplicationController
  before_action :set_question, only: %i[ show edit update destroy ]
  before_action :set_poll, only: %i[ new create index ]

  # GET /polls/1/questions or /polls/1/questions.json
  def index
    @questions = @poll.questions.all
  end

  # GET /questions/1  or /polls/1/questions/1.json
  def show
  end

  # GET /polls/1/questions/new
  def new
    # build is just an alias of new for legacy compatibility with Rails 2...
    # its about time that we ditch it
    @question = @poll.questions.new 
    3.times { @question.options.new } # 5 different options 
  end
  
  # GET /questions/1/edit
  def edit
  end

  # POST /polls/1/questions or /polls/1/questions.json
  def create
    @question = @poll.questions.new(question_params)
    respond_to do |format|
      if @question.save
        format.html { redirect_to @question, notice: "Question was successfully created." }
        format.json { render :show, status: :created, location: @question }
      else
        format.html { render :new, status: :unprocessable_entity }
        format.json { render json: @question.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /questions/1 or /questions/1.json
  def update
    respond_to do |format|
      if @question.update(question_params)
        format.html { redirect_to @question, notice: "Question was successfully updated." }
        format.json { render :show, status: :ok, location: @question }
      else
        format.html { render :edit, status: :unprocessable_entity }
        format.json { render json: @question.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /questions/1 or /questions/2.json
  def destroy
    session[:return_to] ||= request.referer 
    @question.destroy
    respond_to do |format|
      format.html { redirect_to session.delete(:return_to), notice: "Question was successfully destroyed." }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_question
      @question = Questions.find(params[:id])
    end

    # Only allow a list of trusted parameters through.
    def question_params
      # do not write this in a single unreadable line
      params.require(:question).permit(
        :question_type, 
        :title, 
        :description,
        :randomize_selection, 
        :voter_abstain, 
        # do not wrap hash arguments in brackets 
        # as it will break if/when the `permit` method is changed to use real keyword arguments 
        # for has_many assocations the key naming convention is also plural_attributes
        options_attributes: [
          :party_id, 
          :title, 
          :description
        ]
      )
    end

    def set_poll
      @poll = Poll.find_by(params[:poll_id])
    end
end

这里的关键区别在于，您应该通过URL中的参数查找嵌套路由的参数，并从轮询实例中创建问题（设置poll_id） 。

添加：

您实际上并未使用在控制器中初始化的模型。如果您想从完全不同的操作中渲染表单，则需要在那里初始化实例变量：

class PollsController < ApplicationController

  def show
    @question = @poll.questions.new
    3.times { @question.options.new } # 5 different options ???
  end
  # ...
end

<%= render "questions/form", question: @question %>

在部分中，您有一个偷偷摸摸的小错误。 Ruby是案例敏感的，因此@poll和@poll实际上是不同的变量。

irb(main):049:0> @foo = "bar"                                                                                                                                                                                 => "bar"
irb(main):050:0> @Foo
=> nil          

由于实例变量被自动透露，因此您只会得到意外的零而不是错误。您实际想要的是：

<%= form_with(model: [@poll, question] ) do |form| %>