通過Rails 4中的關聯，聯接表和has_many出現問題

Question

伙計們，這是我的數據庫結構。 AccountGrade.rb MODEL其帳戶和成績模型的聯接表

class AccountGrade < ActiveRecord::Base
  belongs_to :account
  belongs_to :grade
  attr_accessor :grade
  attr_accessor :section
end

我的account.rb模型

class Account < ActiveRecord::Base
  has_many :grades, :through => :account_grades
  has_many :account_grades
  belongs_to :user
  validates :school_name,:line_1,:city,:state,:country,:pincode,:phone_number, :presence => true
  validates :pincode,:phone_number,numericality: { only_integer: true }
end

我的grade.rb模型

class Grade < ActiveRecord::Base
  has_many :accounts, :through => :account_grades
  has_many :account_grades
  attr_accessor :account_grades
end

我的grades_controller.rb

class GradesController < ApplicationController
  def index
    @grades = Grade.all
    render json: {
      Grades:@grades
    }.to_json
  end

  def add_class_sections
    # unless params[:section]
      @account_grades = AccountGrade.new class_sections_params
      puts "Grades are #{@account_grades}"

      @grades.each do |grade|
        @account_grades = grade
        puts grade
        puts @account_grades
      end
    # end #unless ends here
  end #function add_class_sections ends here


  private

    def class_sections_params
      params.permit!
      # params.require(:gardes).permit(:section)#, :email, :password, :salt, :encrypted_password)
    end

end #class ends here

我在終端跟蹤中收到以下錯誤。

Started POST "/add_classes?grade_id[0]=1&section[0]=2&grade_id[1]=2&section[1]=1&grade_id[2]=3&section[2]=1" for 127.0.0.1 at 2015-11-17 12:43:47 +0530
  ActiveRecord::SchemaMigration Load (0.1ms)  SELECT `schema_migrations`.* FROM `schema_migrations`
Processing by GradesController#add_class_sections as */*
  Parameters: {"grade_id"=>{"0"=>"1", "1"=>"2", "2"=>"3"}, "section"=>{"0"=>"2", "1"=>"1", "2"=>"1"}}
Completed 500 Internal Server Error in 10ms (ActiveRecord: 0.8ms)

ActiveRecord::UnknownAttributeError (unknown attribute 'controller' for AccountGrade.):
  app/controllers/grades_controller.rb:11:in `add_class_sections'


  Rendered /home/anjan/.rvm/gems/ruby-2.2.1/gems/actionpack-4.2.4/lib/action_dispatch/middleware/templates/rescues/_source.erb (11.0ms)
  Rendered /home/anjan/.rvm/gems/ruby-2.2.1/gems/actionpack-4.2.4/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (1.7ms)
  Rendered /home/anjan/.rvm/gems/ruby-2.2.1/gems/actionpack-4.2.4/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (0.9ms)
  Rendered /home/anjan/.rvm/gems/ruby-2.2.1/gems/actionpack-4.2.4/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout (24.8ms)

Answer 1

哇，您的代碼有很多問題。

不管您的推理如何，這都是您應該如何使它工作的...

---

#app/controllers/grades_controller.rb
class GradesController < ApplicationController
    def index
      @grades = Grade.all
      respond_to do |format|
         format.json { render json: @grades.to_json }
         format.html
      end
    end

    def create
      @account_grades = AccountGrade.new class_sections_params
      redirect_to @account.grades if @account_grades.save
    end

  private

    def sections_params
      params.require(:grades).permit(:section)
    end
end

如果您可以使用此代碼，那么您將可以更輕松地了解為什么它要尋找controller屬性（這是一個奇怪的錯誤）。

您還應該了解Rails中的一些約定：

1. 不要使用puts在控制器 -你有Rails.logger.info()輸出到控制台。
2. 讓您的動作保持安靜 -盡管這可能並且經常會破壞，但是Rails控制器的寧靜特性應該是遵循的首要約定。 除非確實需要，否則不要調用add_class_section ，而是應根據需要使用new和create方法。

-

另外， 刪除所有attr_accessor引用 ，尤其是與任何關聯名稱沖突的引用 。

attr_accessor基本上為模型聲明了新的getter / setter方法。 如果這些方法重寫了任何關系，則實際上將阻止它們起作用。

除非要創建一個半永久屬性（即不保存到數據庫的IE），否則不需要attr_accessor 。 Rails中attr_accessor的最常見用法是創建虛擬屬性 ：

Answer 2

這是我想要實現的。 歡迎提供有關重構或改善以下代碼的任何建議。

class GradesController < ApplicationController
  before_filter :authenticate, only: [:create]

    def index
      @grades = Grade.all
      render json: @grades.to_json
    end

    def create
      @section_name_counter = 0
      @section_names=["A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S",
                     "T","U","V","W","X","Y","Z"]
      @account_grades = AccountGrade.new #sections_params
      @account_grades.grade_id = params[:grade_id]
      @account_grades.account_id = params[:account_id]
      @account_grades.save!

      while @section_name_counter < params[:section].to_i do
        @section = Section.new
        @section.account_grade_id = @account_grades.id
        @section.name = @section_names[@section_name_counter]
        @section.save!
        @section_name_counter += 1
      end
      render json: @account_grades if @section.save
    end

  private

    def sections_params
      params.require(:grade_id).permit(:section,:account_id)
    end
end