模型具有基於查詢的屬性（N + 1）

Question

我有下一個型號。 它具有基於查詢的屬性。 因為當我在我的應用程序上顯示記錄時，我有N + 1問題。

執行Dish.all.includes(:entries)將無法正常工作，因為此部分from_today.from_current_time查詢的from_today.from_current_time 。

class Dish < ApplicationRecord
  has_many :entries, dependent: :destroy

  belongs_to :user
  belongs_to :category

  before_validation :init, on: :create

  def available?
   current_entry = entries.from_today.from_current_time
   return false if current_entry.count.zero?
   current_entry.first.dishes_left.positive?
  end

end

Answer 1

您可以添加與條件的關聯：

class Dish < ApplicationRecord
  has_many :entries
  has_many :entries_from_today,
    -> { merge(Entry.from_today) },
    class_name: 'Entry'

之后你可能會這樣：

dishes = Dish.all.includes(:entries_from_today)
dishes.each do |dish|
  puts dish.entries_from_today
end