ruby-on-rails - 多対多で中間テーブルの列を取得するには?

Question

領収書インスタンスから数量を取得する方法は?

3 つのテーブルがあり
ます。

class Receipt
  # columns: id, place
  has_many :receipt_foods
  has_many :foods, through: :receipt_food
end

class ReceiptFood
  # columns: id, quantity, receipt_id, food_id
  belongs_to :receipt
  belongs_to :food
end

class Food
  # columns: id, name
  has_many :receipt_foods
  has_many :receipts, through: :receipt_food
end

そのようにjsonに応答したい：

{ "receipts": [
  "receipt": {
     "id": 1,
     "place": "supermarket",
     "foods": [ {
        "food": {
           "id": 1,
           "quantity": 12, // how to echo this ?
           "name": "apple" } 
....
  }

Answer 1

次のような数量を取得できます

receipt_foods = @receipt.receipt_foods 
receipt_foods.each do |receipt_food|
  puts receipt_food.quantity 
end