的has_many通过访问加盟形式表属性

Question

我有以下型号：

class RandomExam < ActiveRecord::Base 
    has_many :random_exam_sections 
    has_many :sections, :through => :random_exam_sections 
end 

class Section < ActiveRecord::Base 
    has_many :random_exam_sections 
    has_many :random_exams, :through => :random_exam_sections 

class RandomExamSection < ActiveRecord::Base 
    belongs_to :random_exam 
    belongs_to :section 
end 

的想法是有一定的配置，以创建随机考试，所以这个表有助于选择你需要哪些板块，然后还选择的每部分问题的数量，这里有每个表的属性：

RandomExam：名称（字符串），created_at（日期时间）的updated_at（日期时间）

科：名称（字符串），created_at（日期时间），updated_at（日期时间）

RandomExamSection：random_exam_id（整数），SECTION_ID（整数），questions_number（整数）

正如你所看到的每节属性的问题数是RandomExamSections表里面，我想访问的形式从RandomExam控制器显示，这里是我的表格：

<%= form_for (@random_exam) do |f| %> 
    <div class="row"> 

     <div class="input-field col s12"> 
      <%= f.label :name, 'Name' %> 
      <%= f.text_field :name, placeholder: 'Enter the name of the  configuration' %> 
     </div> 

    </div> 

    <% @sections.each do |section| %> 

     <div class="row <%= dom_id(section) %>"> 
      <div class="col s4"> 
       <%= check_box_tag 'random_exam[section_ids][]', section.id, 
       @random_exam.section_ids.include?(section.id), id:  dom_id(section), class: "section-checkbox #{dom_id(section)}" %> 
       <%= label_tag dom_id(section), (raw sanitize  section.name, tags: %w(h2 p strong em a br b i small u ul ol li  blockquote), attributes: %w(id class href)), 
       class: "name #{dom_id(section)}" %> 
      </div class="col s4"> 
      <div> 
       <%= text_field_tag "random_exam[random_questions_numbers][#{section.id}][]", nil, 
            :placeholder => 'Enter the number of questions' %> 
      </div> 

     </div> 
    <% end %> 

    <div class="form-group"> 
     <%= f.submit class: "btn waves-effect waves-light green" %> 
    </div> 

<% end %> 

我的控制器：

def create 
    @random_exam = RandomExam.new(random_exam_params) 
    if @random_exam.save 
    assign_random_questions_number 
    flash[:success] = 'Random configuration created successfully' 
    redirect_to @random_exam 
else 
    flash.now[:danger] = @random_exam.errors.full_messages.to_sentence 
    render 'new' 
end 

def assign_random_questions_number 
    if params[:random_exam][:'random_questions_numbers'] == nil 
    return 
    end 


params[:random_exam][:'section_ids'].each do |key, value| 
    record = RandomExamSection.search_ids(@random_exam.id, key) 

    record.each do |random_exam_section_record| 
    number_of_questions = params[:random_exam][:'random_questions_numbers'][key].first.to_i 
    random_exam_section_record.update(questions_number: number_of_questions) 
    end 
end 

末

我得到一个类型错误：TypeError: nil is not a symbol nor a string当我在方法更新记录assign_random_questions_number

此错误，甚至当我在控制台上运行，这似乎

random = RandomExamSection.first 
random.update(questions_number: 10) 

或者当我运行：

random = RandomExamSection.first 
random.questions_number = 10 
random.save 

编辑

我结束了删除关联我n RandomExamSection并在'assign_random_questions_number'内使用question_number重新创建它

谢谢。

Answer 1

如果使用nested_attributes你可以做这样的事情：

#form 
<h4>Selected exams</h4> 
<%= f.fields_for :random_exam_sections do |b| %> 
    <%= b.hidden_field :section_id %> 
    <%= b.label :selected, b.object.section.name %> 
    <%= b.check_box :selected, { checked: !b.object.id.blank? } %> 
    <br> 
    <%= b.label :question_numbers %> 
    <%= b.text_field :questions_number %> 
<% end %> 

#RandomExamModel 
class RandomExam < ApplicationRecord 
    has_many :random_exam_sections, inverse_of: :random_exam 
    has_many :sections, :through => :random_exam_sections 

    accepts_nested_attributes_for :random_exam_sections, reject_if: :is_not_selected 


    private 
    def is_not_selected(attr) 
    attr["selected"] == '0' 
    end 
end 

# RandomExam 
class RandomExamSection < ApplicationRecord 
    belongs_to :random_exam 
    belongs_to :section 

    attr_accessor :selected 
end 

# Controller 
# GET /random_exams/new 
    def new 
    @random_exam = RandomExam.new 
    @random_exam.random_exam_sections.build(Section.all.map{|s| {section_id: s.id}}) 
    end 

的想法基本上是

- Build on controller the random_exam_sections to be selected 
- Write a form that allows to you 'select' one option and assign the number 
- Then, validate if the random_exam_section of a sections was selected (this why i made that `attr_accessor :selected`, i need a place to write if user select the exam_section) 
- If was selected, save. 

这里的技巧是建立在控制器上，然后选择视图和验证在模型上选择。在这里，我举了一个例子，如果你需要帮助：https://github.com/afromankenobi/nested_attr_demo

要添加部分时，random_exam_sections已被创建，你应该使用JavaScript。也许这个railscasts可以帮助你http://railscasts.com/episodes/196-nested-model-form-part-1