Rails 单表继承 设计助手

Question

我用 Devise 创建了一个User模型，并添加了type列等，因此Student和Teacher的模型可以从中继承。所有这些都很好用。我的Teacher模型与模型Course具有一对多关系，其中存储了有关教师课程的所有数据。

我的问题：设计助手current_user.courses不起作用，因为courses表没有列user_id。如何使current_user能够解析.courses，即使课程中的属性称为teacher_id？

我是 Rails 新手，所以任何帮助将不胜感激！ :)

编辑：改进问题并添加架构和模型。

# schema.rb:
create_table "courses", force: :cascade do |t|
    t.string   "title"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer  "teacher_id"
    t.index ["teacher_id"], name: "index_courses_on_teacher_id"
  end
  create_table "users", force: :cascade do |t|
    t.string   "email",                  default: "", null: false
    t.string   "encrypted_password",     default: "", null: false
    t.string   "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.integer  "sign_in_count",          default: 0,  null: false
    t.datetime "current_sign_in_at"
    t.datetime "last_sign_in_at"
    t.string   "current_sign_in_ip"
    t.string   "last_sign_in_ip"
    t.datetime "created_at",                          null: false
    t.datetime "updated_at",                          null: false
    t.string   "name"
    t.string   "type"
    t.integer  "quiz_session_id"
    t.index ["email"], name: "index_users_on_email", unique: true
    t.index ["quiz_session_id"], name: "index_users_on_quiz_session_id"
    t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
  end
# /app/models/course.rb:
class Course < ApplicationRecord
  belongs_to :teacher
  has_many :students
  delegate :teachers, :students, to: :users
end
# /app/models/user.rb:
class User < ApplicationRecord
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
  has_many :courses
  # Which users subclass the User model
  def self.types
    %w(Teacher Student)
  end
  # Add scopes to the parent models for each child model
  scope :teachers, -> { where(type: 'Teacher') }
  scope :students, -> { where(type: 'Student') }
end
# /app/models/teacher.rb:
class Teacher < User
end

Answer 1

您可以通过以下方式定义自己的帮助程序：

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception
  helper_method :current_teacher, :current_student, 
                :teacher_logged_in?, :student_logged_in?
  private
    def current_teacher
      @current_teacher ||= current_user if user_signed_in? and current_user.class.name == "Teacher"
    end
    def current_student
      @current_student ||= current_user if user_signed_in? and current_user.class.name == "Student"
    end
    def teacher_logged_in?
      @teacher_logged_in ||= user_signed_in? and current_teacher
    end
    def student_logged_in?
      @student_logged_in ||= user_signed_in? and current_student
    end
end

我没有执行这些语法，但我过去写过这样的东西，所以如果你遇到任何语法错误，请把它发布在评论中。

编辑：

看到您更新的模型代码后，我认为将用户模型中的course关联更改为如下所示将对您有用：

has_many :courses, :foreign_key  => "teacher_id"

Answer 2

运行：

rails generate migration AddUserReferenceToCourses user:references

我认为这将创建一个迁移，为课程增加user_id

Answer 3

您可以向课程表添加迁移：

rails g migration add_user_id_to_courses user:references

这将在 course.rb 文件中添加belongs_to :user。然后转到 user.rb 文件并添加：

has_many :courses

此关系将允许您从课程或从用户调用课程。