我正在尝试创建一个 Rails 插件。在大多数情况下，我写的作品。但是，关联存在问题。当我尝试调用关联时，出现此错误:

ActiveRecord::Base doesn't belong in a hierarchy descending from ActiveRecord

目前，插件看起来像这样:

module ControlledVersioning
  module ActsAsVersionable
    extend ActiveSupport::Concern

    included do
      has_many :versions, as: :versionable

      after_create :create_initial_version
    end

    module ClassMethods
      def acts_as_versionable(options = {})

        cattr_accessor :versionable_attributes
        self.versionable_attributes = options[:versionable_attributes]
      end
    end

    private
    def create_initial_version
      version = versions.create
    end
  end
end

ActiveRecord::Base.send :include, ControlledVersioning::ActsAsVersionable

同样，每当我尝试调用关联时都会触发错误消息。我在 after_create 回调中使用调试器并尝试运行:

> versions.create
*** ActiveRecord::Base doesn't belong in a hierarchy descending from ActiveRecord

> versions
*** ActiveRecord::Base doesn't belong in a hierarchy descending from ActiveRecord

> Version.new
#<Version id: nil, versionable_id: nil, versionable_type: nil>

最佳答案

为了使其正常工作，您需要更改代码中的一些内容。

首先，versions 是 rails 的一个保留键盘——你不能与那个名称有关系——(我使用名称 versionings 来使它工作)

此外，您要确保只为想要acts_as_versionable 的模型添加has_many 版本控制 - 意思是，移动has_many :versionings, as: versionable、class_name: 'Version' 和 after_create :create_initial_version 调用 acts_as_versionable 方法。

下面是所有内容的样子:

module ControlledVersioning
  module ActsAsVersionable
    extend ActiveSupport::Concern

    module ClassMethods
      def acts_as_versionable(options = {})
        has_many :versionings, as: :versionable, class_name: 'Version'
        after_create :create_initial_version

        cattr_accessor :versionable_attributes
        self.versionable_attributes = options[:versionable_attributes]
      end
    end

    private

    def create_initial_version
      version = versionings.create
    end
  end
end

ActiveRecord::Base.send :include, ControlledVersioning::ActsAsVersionable

做这些改变使插件对我有用:

irb(main):003:0> Post.create!
   (0.1ms)  begin transaction
  Post Create (0.7ms)  INSERT INTO "posts" ("created_at", "updated_at") VALUES (?, ?)  [["created_at", "2019-07-16 08:55:13.768196"], ["updated_at", "2019-07-16 08:55:13.768196"]]
  Version Create (0.2ms)  INSERT INTO "versions" ("versionable_type", "versionable_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["versionable_type", "Post"], ["versionable_id", 3], ["created_at", "2019-07-16 08:55:13.772246"], ["updated_at", "2019-07-16 08:55:13.772246"]]
   (2.0ms)  commit transaction
=> #<Post id: 3, created_at: "2019-07-16 08:55:13", updated_at: "2019-07-16 08:55:13", name: nil>
irb(main):004:0> Post.last.versionings
  Post Load (0.2ms)  SELECT  "posts".* FROM "posts" ORDER BY "posts"."id" DESC LIMIT ?  [["LIMIT", 1]]
  Version Load (0.2ms)  SELECT  "versions".* FROM "versions" WHERE "versions"."versionable_id" = ? AND "versions"."versionable_type" = ? LIMIT ?  [["versionable_id", 3], ["versionable_type", "Post"], ["LIMIT", 11]]
=> #<ActiveRecord::Associations::CollectionProxy [#<Version id: 2, versionable_type: "Post", versionable_id: 3, created_at: "2019-07-16 08:55:13", updated_at: "2019-07-16 08:55:13">]>
irb(main):005:0> 

关于ruby-on-rails - ActiveRecord::Base 不属于从 ActiveRecord 降级的层次结构，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21360392/