has many through

gistfile1.txt

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