Ruby on Rails：模型与多个外键关联 [英] Ruby on Rails: Model Association with multiple foreign keys

问题描述

我正在研究 User 模型，每个用户都应该能够同时拥有学生和教师。但由于 和教师都是 User 的类型，我的模型有点复杂。

这是我现在想尝试的。

Teacher_student_link
$ b

  class TeacherStudentLink< ActiveRecord :: Base 
 attr_accessible：student_id，：teacher_id，：user_id 
 
 belongs_to：user 
 belongs_to：teacher，：class_name => User
 belongs_to：student，：class_name => User
 end 
  

用户 b
$ b

  class User< ActiveRecord :: Base 
 has_many：teacher_student_links，：foreign_key => {：student_id，：teacher_id}，：dependent => ：destroy 
 has_many：students，：through => ：teacher_student_links 
 has_many：teachers，：through => ：teacher_student_links 
 end 
  

如果一切都按我的意图工作，我应该能够

  @user = User.new 
 @ user.students 
 @ user.teachers 
 @ user.student.teachers 
  

我认为上面唯一的问题是我不能给两个外国人键同时 teacher_student_link ，但我不确定。作为解决方法，我没有在我的模型中的teacher_id，只是 student.user 调用老师。任何人都可以帮助我解决这个问题？

更新：
使用以下解决方案如何创建新链接？ / p>

  def become_student 
 @user = user.find（params [：id]）
 @student_link = @ user.student_links.create（：student_id => current_user.id）
 @teacher_link = current_user.teacher_links.create（：teacher_id => @ user.id）
 end 
  

如果我这样做，是学生和老师配对正确吗？
我困惑一点，因为在TeacherStudentLink中有用户，学生，<$ c $

解决方案

您可以通过以下方式应将teacher_student_links关联分成两个关联：

  has_many：teacher_links，：foreign_key => ：student_id，：dependent => ：destroy，：class_name => TeacherStudentLink
 has_many：student_links，：foreign_key => ：teacher_id，：dependent => ：destroy，：class_name => TeacherStudentLink
 has_many：students，：through => ：student_links 
 has_many：teachers，：through => ：teacher_links 
  

您可能需要将外键添加到TeacherStudentLink上的belongs_to关联

更新：

关于创建链接的第二个问题， p>

  @user = User.find（params [：id]）
 @ user.students< current_user 
  

应该自动创建TeacherStudentLink，如果一切设置正确，您的关联应该工作。 / p>

I am working on a User model, and each user should be able to have both students and teachers. However, since student and teacher are both a type of User, my model got a little complicated.

This is what I am trying right now.

Teacher_student_link

class TeacherStudentLink < ActiveRecord::Base
  attr_accessible :student_id, :teacher_id, :user_id

  belongs_to :user
  belongs_to :teacher, :class_name => "User"
  belongs_to :student, :class_name => "User"
end

User

class User < ActiveRecord::Base
  has_many :teacher_student_links, :foreign_key => { :student_id, :teacher_id }, :dependent => :destroy
  has_many :students, :through => :teacher_student_links
  has_many :teachers, :through => :teacher_student_links
end

If everything works as I intended, I should be able to do

@user = User.new
@user.students
@user.teachers
@user.student.teachers

I think the only problem with above is that I can't give two foreign keys at the same time to teacher_student_link, but I'm not sure. As a workaround, I don't have teacher_id in my model yet, and just doing student.user to call the teacher. Can anyone help me with this issue?

Update: With the solution below, how should I create a new link?

def become_student
  @user = user.find(params[:id])
  @student_link = @user.student_links.create(:student_id => current_user.id)
  @teacher_link = current_user.teacher_links.create(:teacher_id => @user.id)
end

If I do it like this, is the student and teacher paired up correctly? I am confused a little because in the TeacherStudentLink, there are user, student, teacher, and I'm not sure how to deal with creating links.

解决方案

You should separate out the teacher_student_links association into two associations:

  has_many :teacher_links, :foreign_key => :student_id, :dependent => :destroy, :class_name => "TeacherStudentLink"
  has_many :student_links, :foreign_key => :teacher_id, :dependent => :destroy, :class_name => "TeacherStudentLink"
  has_many :students, :through => :student_links
  has_many :teachers, :through => :teacher_links

You might need to add the foreign keys to the belongs_to association on TeacherStudentLink also

Update:

Regarding your second question about creating links, the following should work:

@user = User.find(params[:id])
@user.students << current_user

The TeacherStudentLink should be created automatically, and your associations should work if everything is set up correctly.

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