Rails 3 - has_and_belongs_to_many

Question

I have 2 models - Teacher and Subject. A want to connect them via Join table with name Qualification.

It looks like i

Answer 1

In rails 3 the best way is make intermediate table qualification through migration

the attributes will be like of this table

subject_id:integer teacher_id:integer

and also make class of qualification like this

class Qualification < ActiveRecord::Base
  has_many :subjects
  has_many :teachers
end

and then define other two models like

 class Teacher < ActiveRecord::Base
   has_many :qualifications
   has_many :subjects, :through => :qualifications
 end

 class Subject < ActiveRecord::Base 
  has_many :qualifications
  has_many :teachers, :through => :qualifications
 end

and read this link carefully also

   http://blog.hasmanythrough.com/2007/1/15/basic-rails-association-cardinality