ActiveRecord 与两个不同模型的关联

Question

我很难思考应该如何配置我的表 + 关联。

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

• 一个人的诉讼（@person.lawsuits）；
• 公司诉讼（@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和模型的方式：

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 |

诉讼当事人

| 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

任何帮助将不胜感激......

Answer 1

您在正确的轨道上，但您需要在您的加入模型中引入polymorphic relationship 才能使这种类型的建模工作。 An Enum can handle differentiating between Defendants and Plaintiffs，并免费提供您要求的几种范围/方法。

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 lawsuit_parties 表更改为以下列（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，使用has_many 的:as 选项告诉Rails Person 和Company 记录与许多Lawsuit 相关联。

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）。

一旦您设置了这样的诉讼派对，您就应该准备就绪。