How to properly link tables in Rails?

Question

Ruby on Rails

There are two tables:
hospitals
id | name | ............ | main_doctor_id
doctors
id | fio | ...... | hospital_id
I now bind like this:

Hospital.rb
has_many :doctors
belongs_to :doctor, foreign_key: :main_doctor_id
 
Doctor.rb
belongs_to :hospital

On cyberforum, they suggested to write in Hospital.rb: this thing:
belongs_to :doctor, as: :main_doctor, foreign_key: :main_doctor_id
But for me it swears at the as argument .
Tell me how to connect correctly and how to get main_doctor for each Hospital.

Answer 1

has_many :executors, :class_name => 'Post', :foreign_key => 'executor_id'

something like that...