ruby-on-rails - 如何通过验证预先加载 fields_for

Question

我的表单中有这个 fields_for :

= f.fields_for :parts do |builder|
  = builder.input :body, label: builder.object.another_relation.description, required: false

在主模型中，我有这个验证:

validates_associated :parts

在零件模型中，我有这个验证:

validates :body, presence: true

这很好用。当我将某些部分留空并尝试创建模型时，表单会再次重新显示并显示正确的错误消息。

但是在日志中我看到标签正在查询每个部分的数据库，所以我需要预先加载它。

如何？

这是我的尝试:

= f.fields_for :parts, f.object.parts.includes(:question_part) do |builder|
  = builder.input :body, label: builder.object.another_relation.description, required: false

这种渴望成功加载关系，但是当我将某些字段留空并尝试创建模型时，表单会重新显示，所有部分都为空且没有错误。我认为这是正常的，因为我正在强制 fields_for 从我正在传递的那个集合中加载字段。

有谁知道如何解决这个问题？

Answer 1

这是一种方法。

想象一下这 4 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。而一个答案属于一个问题，并且有 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', dependent: :destroy
  accepts_nested_attributes_for :parts, allow_destroy: true

  # ...
end

class AnswerPart
  belongs_to :answer
  belongs_to :question_part

  validates :body, presence: true

  # ...
end

我们来看看应答 Controller :

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。我已经注释掉了标准方式，同时我正在使用自定义查询检索它(应该移到 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，请发表评论或添加新答案。

现在是模板:

# 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', f: f, 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 %>