Question

我在名为Notifiable的模型中有一个名为Notifiaction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

当我尝试将通知加入通知时（Notification.joins{notifiable} - 它的吱吱声，活动记录代码会产生相同的结果）我收到错误：ActiveRecord::EagerLoadPolymorphicError: Can not eagerly load the polymorphic association :notifiable

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，这些都不是我的情况。可能吗？我错过了什么

Answer 1

您可以使用includes：

来加载两种多态关联

Notification.where(whatever: "condition").includes(:notifiable)

考虑到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。即：

Notification.where(whatever: "condition").includes(:notifiable).map(&:notifiable)
# => [Bill, Balance, etc]

Answer 2

由于您已经宣布了账单和余额关联，您可以加入个人关联并对其进行联盟。

像

这样的东西

scope :billiables_for_account, ->(account) do
  union_scope(joins(:bill).where(bills: {account: account}),
      joins(:balance).where(bills: {account: account}))
end

rails加入多态关联

2 个答案: