ruby-on-rails - Rails 嵌套 has_one : cannot delete existing record

Question

我正在尝试更新“问题”模型中的嵌套 Question_output 属性。一个问题有一个问题输出。 如果数据库中没有现有的question_outputs，则一切正常。但如果记录已经有 Question_output，我在尝试更新时会得到以下信息:

Failed to remove the existing associated question_output. The record failed to save when after its foreign key was set to nil.

我本以为allow_destroy 会解决这个问题，但是唉 - 没有乐趣。诚然，我以前没怎么用过 has_one 。但如果有人对如何解决这个问题有任何想法，我将不胜感激。相关代码如下:

形式:

= form_for [@question.project, @question], :as => :question, :url => admin_project_question_path(@question.project, @question) do |f|
  = render '/shared/form_errors', :model => @question
  = f.fields_for :question_output_attributes do |qo|
    .field
      = qo.label :question_type
      = qo.select :question_type, QuestionOutput::QUESTION_TYPES
    .field
      = qo.label :client_format
      = qo.select :client_format, QuestionOutput::CLIENT_FORMATS
    .field
      = qo.label :required
      = qo.check_box :required
    .field
      = qo.label :min_input, 'Length'
      = qo.text_field :min_length
      = qo.text_field :max_length
    = f.submit 'Save Question Formatting'

问题模型:

class Question < ActiveRecord::Base
  has_one :question_output
  accepts_nested_attributes_for :question_output, :allow_destroy => true
end

问题输出模型:

 class QuestionOutput < ActiveRecord::Base
   belongs_to :question
 end

问题 Controller :

class Admin::QuestionsController < ApplicationController

 def show
   @question = Question.find(params[:id])
   @question.question_output ||= @question.build_question_output
 end 

 def update
    @question = Question.find(params[:id])
    if @question.update_attributes(params[:question])
      flash[:notice] = t('models.update.success', :model => "Question")
      redirect_to admin_project_question_path(@question.project, @question)
    else
      flash[:alert] = t('models.update.failure', :model => "Question")
      redirect_to admin_project_question_path(@question.project, @question)
    end
  end
end

Answer 1

在您的问题模型中将 has_one 行更改为:

has_one :question_output, :dependent => :destroy

accepts_nested_attributes 上的 :allow_destroy => true 允许您通过 _destroy=1 HTML 从问题表单中删除 Question_output属性。

当您删除问题时，:dependent => :destroy 会删除 Question_output。 或者在您的情况下在 Question_output 被新输出替换时将其删除。