ruby-on-rails - rails 加入多态关联

Question

我有一个名为 Notifiable 的多态关联在名为 Notifiaction 的模型中:

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

当我尝试将通知与可通知(Notification.joins{notifiable} - 它是尖叫声，事件记录代码将具有相同的结果)加入通知时，我收到错误:ActiveRecord::EagerLoadPolymorphicError: Can not eagerly load the polymorphic association :notifiable
我看过一些关于这个异常(exception)的帖子，但是当我尝试加入表格时，没有一个是我的情况。是否可以？我错过了什么

Answer 1

您可以使用包含来预先加载两个多态关联:

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

考虑到 Bill 和 Balance 结果都匹配查询结果，include 应该在查询结果中预加载这两个模型。 IE:

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