餐厅 has_many 菜
Dish
has_many Photo
Photo
belongs_to Dish
Restaurant 1
Dish 1
Photo 1 May 9, 1:00 PM
Dish 2
Photo 2 May 9, 2:00 PM
Dish 3
Photo 3 May 9, 3:00 PM
Restaurant 2
Dish 4
Photo 4 May 9, 1:00 PM
Dish 5
Photo 5 May 9, 2:00 PM
Dish 6
Photo 6 May 9, 3:00 PM
我正在尝试检索最新的 50 张照片,每家餐厅限制为 2 张菜肴照片。鉴于上面的数据,我将能够检索带有 ids 的照片2, 3, 5, and 6
我目前的实现至少可以说是丑陋的。
hash = {}
bucket = []
Photo.includes(:dish => [:restaurant]).order("created_at desc").each do |p|
restaurant_id = p.dish.restaurant.id
restaurant_count = hash[restaurant_id].present? ? hash[restaurant_id] : 0
if restaurant_count < 2
bucket << p
hash[restaurant_id] = restaurant_count + 1
end
# if you've got 50 items short circuit.
end
我不禁觉得有一个更有效的解决方案。任何想法,将不胜感激 :-)。