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Question

我有以下背景：

4个型号：

项目
投资者
订阅
ExternalSubscription

project在investors或subscriptions之间应有多个external_subscriptions。

我目前有一个类似这样的方法：Investor.where(id: (subscription_ids + external_subscription_ids))。

我的目标是建立has_many关系（并准确使用has_many activerecord功能）以获得相同的结果。我该如何实现这一目标？它甚至可能吗？

谢谢！

Project

[Associations]
  has_many :subscriptions
  has_many :external_subscriptions

[Table description]
  create_table "projects", force: :cascade do |t|
    t.string "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

Investor

[Associations]
  has_many :subscriptions
  has_many :external_subscriptions

[Table description]
  create_table "investors", force: :cascade do |t|
    t.string "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

Subscription

[Associations]
  belongs_to :project
  belongs_to :investor

[Table description]
  create_table "subscriptions", force: :cascade do |t|
    t.integer "project_id"
    t.integer "investor_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["investor_id"], name: "index_subscriptions_on_investor_id"
    t.index ["project_id"], name: "index_subscriptions_on_project_id"
  end

ExternalSubscription

[Associations]
  belongs_to :project
  belongs_to :investor

[Table description]
  create_table "external_subscriptions", force: :cascade do |t|
    t.integer "project_id"
    t.integer "investor_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["investor_id"], name: "index_external_subscriptions_on_investor_id"
    t.index ["project_id"], name: "index_external_subscriptions_on_project_id"
  end

我在rails 5.0.x上

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我的真实模型比这更复杂。在这里，我只是展示关系以便于讨论，但我无法将subscriptions和external_subscriptions合并到同一个模型中。

Answer 1

由于您的订阅和external_subscriptions似乎不需要不同的信息（两个表都有相同的字段），我只使用一个模型和表，并根据表中的新字段对订阅进行分类。通过使用适当的范围，您可以轻松访问所有相关模型。

<强>项目

class Project < ApplicationRecord
  has_many :subscriptions
  has_many :external_subscriptions, -> { external }, class_name: "Subscription"
  has_many :normal_subscriptions, -> { normal }, class_name: "Subscription"
  has_many :investors, through: :subscriptions
  has_many :external_investors, through: :external_subscriptions, :source => :investor
  has_many :normal_investors, through: :normal_subscriptions, :source => :investor

end

<强>投资者

class Investor < ApplicationRecord
  has_many :subscriptions
  has_many :projects, through: : subscriptions
end

<强>订阅

class Subscription < ApplicationRecord
  belongs_to :project
  belongs_to :investor
  enum type: [ :external, :normal ]

  scope :external, -> { where(type: :external) }
  scope :normal, -> { where(type: :normal) } 
end

然后您可以访问不同的项目投资者：

project = Project.first.
project.investors #all
project.external_investors #only external
project.normal_investors #only normal

Answer 2

由于@ MrYoshiji的评论，我通过执行UNION的SQL视图解决了我的问题。

这是POC：https://github.com/yoones/rails-has_many-through-view

ActiveRecord has_many通过两个模型

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2 个答案: