Rails 可以在多个 table 中引用用户 table 中的枚举角色列吗？

Question

我有一个带有角色属性的用户模型，我使用枚举定义了它。

enum role: {'Instructor': 0, 'Student': 1, 'Other': 2}

现在，我有另一位 table 讲师，来自用户 table。

我有一门课程 table 有讲师的参考资料。

我只希望讲师创建课程，不需要任何其他角色。

我正在使用 Pundit 进行授权。我在创建新课程时遇到问题。

def create
  ...
  authorize @course

  @course.instructor = Instructor.where(user: current_user).first

以上查询正在回滚但不保存课程。

任何建议都会有更大的帮助。

app/policies/course_policy.rb

Rollback Error

app/policies/course_policy.rb

 class CoursePolicy < ApplicationPolicy
  attr_reader :user, :model

  def initialize (user, model)
    @user = user
    @course = model
  end

  def index?
    true
  end

  def show?
    true
  end

  def create?
    @user.Instructor?
  end

  def update?
    @user.Instructor_of? @course
  end

  class Scope
    attr_reader :user, :scope

    def initialize(user, scope)
      @user = user
      @scope = scope
    end

    def resolve
      scope.all
    end
  end
end

回滚错误输出：

ActiveRecord::AssociationTypeMismatch (Instructor(#70064238051700) expected, got #<ActiveRecord::Relation []> which is an instance of Instructor::ActiveRecord_Relation(#70064238083180)):

app/controllers/courses_controller.rb:31:in `create'
Started POST "/courses" for ::1 at 2019-04-13 06:02:33 +0700
Processing by CoursesController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"++6oBiY4MeOHZKyMwAJ8VqF9ACayve5e+cmMg7FqG4dbHVCfDpI3uqVK7g75+auf8OABUTEnXlm9jshWu/50EQ==", "course"=>{"name"=>"Ruby on Rails", "description"=>"jk.jlliyf", "start_date(1i)"=>"2019", "start_date(2i)"=>"4", "start_date(3i)"=>"12", "end_date(1i)"=>"2019", "end_date(2i)"=>"7", "end_date(3i)"=>"12"}, "commit"=>"Create Course"}
  User Load (0.7ms)  SELECT  "users".* FROM "users" WHERE "users"."id" =  ORDER BY "users"."id" ASC LIMIT   [["id", 2], ["LIMIT", 1]]
  ↳ /home/sagar/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/activerecord-5.2.3/lib/active_record/log_subscriber.rb:98
  Instructor Load (1.8ms)  SELECT  "instructors".* FROM "instructors" WHERE "instructors"."user_id" =  ORDER BY "instructors"."id" ASC LIMIT   [["user_id", 2], ["LIMIT", 1]]
  ↳ app/controllers/courses_controller.rb:31
   (0.4ms)  BEGIN
  ↳ app/controllers/courses_controller.rb:34
   (0.4ms)  ROLLBACK
  ↳ app/controllers/courses_controller.rb:34
  Rendering courses/new.html.erb within layouts/application
  Rendered courses/_form.html.erb (44.0ms)
  Rendered courses/new.html.erb within layouts/application (46.7ms)
Completed 200 OK in 267ms (Views: 124.6ms | ActiveRecord: 32.4ms)

课程模型：

app/models/course.rb

    class Course < ApplicationRecord
        belongs_to :instructor
    end

Answer 1

根据评论线程，似乎没有必要使用 Instructor 模型。

因为在您的策略中，您已经将 create 操作限制为具有 Instructor 角色的 user，并且您从不期望 Instructor 具有属性超过 user_id，那么我想我会做：

def create
  ...
  authorize @course
  @course.instructor = current_user
  ...
end

现在，我打赌 Course 有 instructor_id，而不是 user_id。但是，没关系。您只需要做：

class Course << ApplicationRecord 

  belongs_to :instructor, class_name: 'User' # or whatever your user class name is.

  ...

end

现在您将能够做到：

@course.instructor

并取回作为课程讲师的 User。

我还打赌 Instructor has_many :courses 通常允许您执行以下操作：

@instructor.courses

所以，您需要做的是：

class User << ApplicationRecord 

  has_many :instructed_courses, class_name: 'Course', foreign_key: :instructor_id

  ...

end

现在您可以执行以下操作：

@user.instructed_courses
current_user.instructed_courses

我正在做 "instructed_courses" 因为据推测，具有 Student 角色的 User 会想要做类似的事情：

@user.enrolled_courses

要做到这一点，我想我会创建：

class StudentCourse < Application 

    belongs_to :enrolled_course, class_name: 'Course'
    belongs_to :student, class_name: 'User' 

end

然后：

class User << ApplicationRecord 

  has_many :instructed_courses, class_name: 'Course', foreign_key: :instructor_id
  has_many :student_courses, foreign_key: :student_id
  has_many :enrolled_courses, through: :student_courses

  ...

end

现在你应该可以做到：

@user.enrolled_courses
current_user.enrolled_courses

您可能还想做类似的事情：

class Course << ApplicationRecord 

  belongs_to :instructor, class_name: 'User' # or whatever your user class name is.
  has_many :student_courses, foreign_key: :enrolled_course_id
  has_many :students, through: :student_courses
  ...

end

这样你就可以做到：

@course.students

沙赞！

Rails 可以在多个 table 中引用用户 table 中的枚举角色列吗？

Rails can a enum role column in User table be referenced in multiple tables?

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rails-migrations

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