[英]rails joins polymorphic association
I have a ploymorphic association named Notifiable
in a model named Notifiaction
: 我在名为
Notifiaction
的模型中有一个名为Notifiable
的ploymorphic关联:
module Notifiable
def self.included(base)
base.instance_eval do
has_many :notifications, :as => :notifiable, :inverse_of => :notifiable, :dependent => :destroy
end
end
end
class Bill < ActiveRecord::Base
include Notifiable
end
class Balance < ActiveRecord::Base
include Notifiable
end
class Notification
belongs_to :notifiable, :polymorphic => true
belongs_to :bill, foreign_key: 'notifiable_id', conditions: "notifiable_type = 'Bill'"
belongs_to :balance, foreign_key: 'notifiable_id', conditions: "notifiable_type = 'Balance'"
end
when I try to join notification with notifiable ( Notification.joins{notifiable}
- it's squeel, active record code will have the same result) I get the error: ActiveRecord::EagerLoadPolymorphicError: Can not eagerly load the polymorphic association :notifiable
当我尝试加入通知时通知(
Notification.joins{notifiable}
notifiable Notification.joins{notifiable}
- 它的吱吱声,活动记录代码会有相同的结果)我得到错误: ActiveRecord::EagerLoadPolymorphicError: Can not eagerly load the polymorphic association :notifiable
I've seen some posts about this exception but none of them was exactly my case when I try to just join the tables. 我已经看过一些有关此异常的帖子,但当我尝试加入表格时,它们都不是我的情况。 Is it possible?
可能吗? what am I missing
我错过了什么
You can eager load both polymorphic associations by using includes: 您可以通过使用includes来急切加载两个多态关联:
Notification.where(whatever: "condition").includes(:notifiable)
Considering both Bill and Balance results match the query result, the include should preload both models in the query result. 考虑Bill和Balance结果与查询结果匹配,include应该在查询结果中预加载两个模型。 ie:
即:
Notification.where(whatever: "condition").includes(:notifiable).map(&:notifiable)
# => [Bill, Balance, etc]
Since you already have the bill and balance associations declared, you Can join individual associations and Do a Union on them. 由于您已经声明了帐单和余额关联,因此您可以加入单个关联并对其进行联盟。
Something like 就像是
scope :billiables_for_account, ->(account) do
union_scope(joins(:bill).where(bills: {account: account}),
joins(:balance).where(bills: {account: account}))
end
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