ActiveRecord 与两个不同模型的关联

Question

我很难思考应该如何配置表 + 关联。

我有一个 Lawsuit 模型。诉讼 has_many 方（被告、原告、律师等）。反过来，派对可以是 Person 或 Company。最终，我希望能够得到：

一个人的官司(@person.lawsuits);
一家公司的官司（@company.lawsuits）；和
诉讼当事人（@lawsuit.parties），可以是people或companies。

这就是我目前设置表格 + 模型的方式：

人

| id | fname  | lname | date_of_birth |
| -- | ------ | ----- | ------------- |
|  1 | John   | Smith |    1974-02-04 |
|  2 | George | Glass |    1963-07-29 |

公司

| id | name      | duns      | ticker | address      |
| -- | --------- | --------- | ------ | ------------ |
|  1 | Acme Inc. | 239423243 | ACME   | 123 Main St. |

诉讼

| id | jurisdiction | court | case_no    | title                       |
| -- | ------------ | ----- | ---------- | --------------------------- |
|  1 |      federal | SDNY  | 18-CV-1234 | Smith v. Glass, Acme, et al |

lawsuit_parties

| id | lawsuit_id | person_id | company_id | role      |
| -- | ---------- | --------- | ---------- | --------- |
|  1 |          1 |         1 |            | plaintiff |
|  2 |          1 |         2 |            | defendant |
|  3 |          1 |           |          1 | defendant |

# models/lawsuit.rb:
class Lawsuit < ApplicationRecord
    has_many :lawsuit_parties

    def parties
        self.lawsuit_parties
    end

    def defendants
        self.parties(where(lawsuit_parties: {role: 'defendant'})
    end

    def plaintiffs
        self.parties(where(lawsuit_parties: {role: 'plaintiff'})
    end

    def attorneys
        self.parties(where(lawsuit_parties: {role: 'attorney'})
    end
end

# models/lawsuit_party.rb
class LawsuitParty < ApplicationRecord
    belongs_to :person
    belongs_to :company
end

# models/person.rb
class Person < ApplicationRecord
    has_many :lawsuit_parties
    has_many :lawsuits, through: :lawsuit_parties
end

# models/company.rb
class Company < ApplicationRecord
    has_many :lawsuit_parties
    has_many :lawsuits, through: :lawsuit_parties
end

如有任何帮助，我们将不胜感激……

Answer 1

您的方向是正确的，但您需要介绍一个 polymorphic relationship onto your Join Model to get this type of modeling to work. An Enum can handle differentiating between Defendants and Plaintiffs，并免费提供几个 scopes/methods。

class LawsuitParty < ApplicationRecord
    belongs_to :lawsuit
    belongs_to :partiable, polymorphic: true

    enum role: [:defendant, :plaintiff]
end

您需要编写迁移以将您的 lawsuit_parties table 更改为以下列（所有 Rails 约定名称）：

partiable_id   = Integer
partiable_type = String
role           = String

lawsuit_parties

| id | lawsuit_id | partiable_id | partiable_type | role      | 
| -- | ---------- | ------------ | -------------- | ----------|
|  1 |          1 |            1 | Person         | defendant |
|  2 |          1 |            2 | Company        | plaintiff |
|  3 |          1 |            1 | Company        | defendant |

接下来，告诉 Rails Person 和 Company 记录与许多使用 has_many 的 :as 的 Lawsuit 相关联选项。

class Person < ApplicationRecord
    has_many :lawsuit_parties, as: :partiable
    has_many :lawsuits, through: :lawsuit_parties
end

将相同的 has_many :lawsuit_parties, as: :partiable 添加到公司，或以后可能出现的任何其他模型（即 Judge 或 JuryMember）。

像这样设置 LawsuitParty 后，您应该就万事大吉了。

ActiveRecord 与两个不同模型的关联

ActiveRecord associations with two different models

ruby

activerecord

ruby-on-rails

polymorphic-associations

ruby-on-rails-5