Using join tables in ruby on rails

Question

Lets say I have two databases: one for students and one for classes. I would like to be able to \'add\' classes to a specific student and also be able to add students to a

Answer 1

Everything true what @Jordan said, here the concrete steps to take:

1. Create a migration: rails g model CourseStudent creates a join model for the n:m relation, and the migration to the corresponding table.

2. Edit the migration file CreateCourseStudent so it contains the following:

   class CreateCourseStudent < ActiveRecord::Migration
     def change
       create_table :course_students do |t|
   
         # Your code comes here
         t.integer :student_id
         t.integer :course_id
   
         # Here comes the generated code 
         t.timestamps
       end
     end
   end
   

3. Run the migration: rake db:migrate. As a result, the join table should now exist in your database.

4. Add to the models the following code

   class Course < ActiveRecord::Base
     has_many :course_students
     has_many :students, :through => :course_students
   end
   
   class Student < ActiveRecord::Base
     has_many :course_students
     has_many :courses, :through => :course_students
   end
   
   class CourseStudent < ActiveRecord::Base
     belongs_to :student
     belongs_to :course
   end
   

You are now able to use the methods generated by the methods belongs_to and has_many:

• @course.students
• @student.courses

Try to find all the relevant facts and snippets in the Rails Guides, there you should find all information you need to get on track. Good luck!