I’m trying to figure out the correct “Rails” way to perform validation prior to creating a new assocation between my models. Here’s the models:
class User < ActiveRecord::Base
has_many :instructed_courses, :through => :instructorships, :source => :course
class Course < ActiveRecord::Base
has_many :instructors, :through => :instructorships, :source => :instructor
class Instructorship < ActiveRecord::Base
belongs_to :instructor, :class_name => ‘User’, :foreign_key => ‘user_id’
I’m trying to introduce a validation whereby only user objects with a role of ‘instructor’ can be assigned as an instructor on a course.
Firstly, where would this validation go? On the association model? And secondly, what is the right way to set this up?
thanks for your help,