的has_many通過訪問加盟形式表屬性

Question

我有以下型號：

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，以創建隨機考試，所以這個表有助於選擇你需要哪些板塊，然後還選擇的每部分問題的數量，這裏有每個表的屬性：

RandomExam：名稱（字符串），created_at（日期時間）的updated_at（日期時間）

科：名稱（字符串），created_at（日期時間），updated_at（日期時間）

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

正如你所看到的每節屬性的問題數是RandomExamSections表裏面，我想訪問的形式從RandomExam控制器顯示，這裏是我的表格：

<%= 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

我得到一個類型錯誤：TypeError: nil is not a symbol nor a string當我在方法更新記錄assign_random_questions_number

此錯誤，甚至當我在控制檯上運行，這似乎

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

或者當我運行：

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

編輯

我結束了刪除關聯我n RandomExamSection並在'assign_random_questions_number'內使用question_number重新創建它

謝謝。

Answer 1

如果使用nested_attributes你可以做這樣的事情：

#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. 

這裏的技巧是建立在控制器上，然後選擇視圖和驗證在模型上選擇。在這裏，我舉了一個例子，如果你需要幫助：https://github.com/afromankenobi/nested_attr_demo

要添加部分時，random_exam_sections已被創建，你應該使用JavaScript。也許這個railscasts可以幫助你http://railscasts.com/episodes/196-nested-model-form-part-1