如何通过一个查询访问两个多态关联？答案

【问题标题】：How to access two polymorphic associations with one query?如何通过一个查询访问两个多态关联？
【发布时间】：2020-08-17 08:27:58
【问题描述】：

在我的 Rails 6 应用程序中，我有这些模型：

class Account < ApplicationRecord

  has_many :carriers
  has_many :clients

  # Unfortunately, these two don't work together. I have to uncomment one of them to get the other one to work:
  has_many :people, :through => :carriers # works but omits clients
  has_many :people, :through => :clients # works but omits carriers

end

class Carrier < ApplicationRecord

  belongs_to :account

  has_many :people, :as => :personalizable

end

class Client < ApplicationRecord
  
  belongs_to :account

  has_many :people, :as => :personalizable

end

class Person < ApplicationRecord

  belongs_to :personalizable, :polymorphic => true

end

如何在一个查询中访问帐户的carriers 和 clients？

我很想做account.people 之类的操作来向所有该帐户的人展示，但还没有找到实现这一目标的方法。

怎么做？

【问题讨论】：

has_many :people, -> { joins(:carriers, :clients) }"' 适合你吗？
不，@benjessop，不幸的是它没有。我收到此错误：ActiveRecord::ConfigurationError (Can't join 'Person' to association named 'carriers'; perhaps you misspelled it?)

标签： ruby-on-rails ruby activerecord

【解决方案1】：

您不能对两个关联使用相同的方法名称，而是可以将其重命名为 carrier_people 和 client_people 并立即加载两者。

class Account < ApplicationRecord

  has_many :carriers
  has_many :clients

  has_many :carrier_people, :through => :carriers, source: :people # works but omits clients
  has_many :client_people, :through => :clients, source: :people # works but omits carriers

end

您可以像这样急切加载。

Account.includes(:carrier_people, :client_people)

【讨论】：

谢谢。但是如何过滤关联？我尝试了类似Account.includes(:carrier_people, :client_people).people.where(:first_name => "John") 的东西，但它给了我一个错误：NoMethodError (undefined method 'people' for #<Account::ActiveRecord_Relation:0x00007fe4e46f71d0>)
您可以这样做，Account.includes(:carrier_people, :client_people).where(carrier_people: {first_name: "John"}).or(Account.includes(:carrier_people, :client_people)。 where(client_people: {first_name: "John"}))
哇，比我想象的要复杂！