Rails has_many通过关联问题

Question

I have 3 models:

sophead
od 
od_item

sophead has many ods and od has many od_items .

each od_item belongs to one od and each od belongs to one sophead

I want to be able to return all od_items for a specific sophead like this:

all_od_items_for_first_sophead = Sophead.first.od_items

what is the correct association for getting all the od_item s for a sophead ?

I had tried:

has_many :od_items, through: :ods

but I believe that this is incorrect as it doesn't really match this diagram - in that diagram's example (with different model names), the arrow from patients to appointments would run the other direction.

Thanks in advance

Answer 1

Your try was correct way to do it. Your models must have associations like this:

models/sophead.rb

class Sophead < ApplicationRecord
  has_many :ods
  has_many :od_items, through: :ods
end

models/od.rb

class Od < ApplicationRecord
  belongs_to :sophead
  has_many :od_items
end

models/od_item.rb

class OdItem < ApplicationRecord
  belongs_to :od
end