定义两个模型之间的关系

Question

I have a CourseSession model. Each CourseSession has some lessons .

I would like to call: lesson.course_session and get the CourseSession that refers to the lesson .

I don't want to use a foreign key in order to practice rails.

How can I connect between them? Every Lesson has a unique effective_date column that coresponds to an effective_date in the CourseSession model.

So how do I define the associations in order to achieve lesson.course_session ?

Answer 1

It is possible, I guess, but not an advised approach. If it's for the sake of learning something new, go ahead. But anyway, in the Lesson model, use:

belongs_to :course_session, primary_key: :effective_date, foreign_key: :effective_date

And in CourseSession:

has_many :lessons, primary_key: :effective_date, foreign_key: :effective_date

Found a post here talking about this: Belongs_to primary key?

Take a look at https://apidock.com/rails/ActiveRecord/Associations/ClassMethods/belongs_to under Options/:primary_key