ruby-on-rails – 如何通过验证来急切加载fields_for

想象一下这四个模型,与StackOverflow等问答网站相关,所以每个人都知道我们在说什么:)

所以,一个问题有N个部分,也有N个答案.虽然答案属于一个问题,但有N个部分.最后,答案部分属于问题部分.

class Question
  has_many :parts,class_name: 'QuestionPart',dependent: :destroy
  accepts_nested_attributes_for :parts,allow_destroy: true
  has_many :answers,dependent: :destroy

  # ...
end

class QuestionPart
  belongs_to :question

  # ...
end

class Answer
  belongs_to :question
  belongs_to :user
  has_many :parts,class_name: 'AnswerPart',allow_destroy: true

  # ...
end

class AnswerPart
  belongs_to :answer
  belongs_to :question_part

  validates :body,presence: true

  # ...
end

我们来看看答案控制器：

class AnswersController < ApplicationController
  def new
    @question = Question.find(params[:question_id)
    @answer = @question.answers.new
    @question.parts.each { |p| @answer.parts.build(question_part: p) }
  end

  def edit
    @answer = Answer.find(params[:id])
    @answer_parts = @answer.parts.includes(:question_part)
  end

  def create
    @question = Question.find(params[:question_id])
    @answer = current_user.answers.build(answer_params.merge(question: @question))

    if @answer.save
      redirect_to @question,notice: 'The answer was successfully created.'
    else
      render :new
    end
  end

  def update
    #@answer = Answer.find(params[:id])
    @answer = Answer.where(id: params[:id]).includes(parts: [:question_part]).first

    if @answer.update(answer_params)
      redirect_to @answer.question,notice: 'The answer was successfully updated.'
    else
      render :edit
    end
  end

  private

  def answer_params
    params.require(:answer).permit(:body,parts_attributes: [:id,:question_part_id,:body])
  end
end

请注意我如何在更新方法中检索答案.我已经注释了标准方式,而我正在使用自定义查询检索它(应该将其移动到Answer模型中).这是我遇到麻烦的地方.如果有人知道更好的方法,只需评论或添加新的答案.

现在为模板：

# new.html.erb
...
<%= form_for [@question,@answer] do |f|
  <%= render 'form',f: f,parts: @answer.parts
<% end %>

# edit.html.erb
...
<%= form_for [@answer] do |f|
  <%= render 'form',parts: @answer_parts || @answer.parts
<% end %>

# _form.html.erb
...
<%= f.fields_for :parts,parts do |builder| %>
  <%= builder.text_field :body,label: builder.object.question_part.description,required: false
  <%= builder.hidden_field :question_part_id %>  
<% end %>