[英]Model has a attribute based on a query (N+1)
I have the next model. 我有下一个型号。 It has an attribute base on a query. 它具有基于查询的属性。 Because that attribute I have the N+1 problem when I show the record on my application. 因为当我在我的应用程序上显示记录时,我有N + 1问题。
Doing Dish.all.includes(:entries)
will not work because this section from_today.from_current_time
of the query. 执行Dish.all.includes(:entries)
将无法正常工作,因为此部分from_today.from_current_time
查询的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
You may add an association with an condition: 您可以添加与条件的关联:
class Dish < ApplicationRecord
has_many :entries
has_many :entries_from_today,
-> { merge(Entry.from_today) },
class_name: 'Entry'
After that you may do like this: 之后你可能会这样:
dishes = Dish.all.includes(:entries_from_today)
dishes.each do |dish|
puts dish.entries_from_today
end
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