棘手的活动记录关系 - 多态双向自引用

Question

您将如何对出版物（文章、书籍、章节等）的引用和引用建模？

出版物可以是一篇文章、一本书或一章，它有许多对其他出版物的引用，其他出版物也引用它（称为这些引文）

我需要能够列出出版物之间的关系：出版物中的引用以及其他出版物对该出版物的引用

我最初的理解是，这将是一种处理不同类型出版物的多态关系，并且需要双向自连接。

我的努力

Publication
belongs_to :writing, :polymorphic =>true
has_and_belongs_to_many :references 
   :class_name => "Publication"
   :join_table => 'reference_citation' 
   :foreign_key => 'reference_id'
   :foreign_key => 'citation_id'

Book,    Chapter,    Article all have:
has_many :publications :as =>writing

我觉得这有点令人困惑，所以任何有助于澄清它的建议都会很棒。甚至对象和字段命名建议。

[我问了这个问题的不太清楚的版本here。]

我也可能需要使用has many through 因为我需要破坏关系的能力

Answer 1

这是一个使用单表继承的自引用关系的解决方案。使用这些命令来创建应用程序：

$ rails myproject
$ cd myproject
$ script/generate model publication type:string name:string
$ script/generate model citation publication_id:integer reference_id:integer

以这种方式设置关系：

class Publication < ActiveRecord::Base
  has_many :citations
  has_many :cited_publications, :through => :citations, :source => :reference
  has_many :references, :foreign_key => "reference_id", :class_name => "Citation"
  has_many :refered_publications, :through => :references, :source => :publication
end

class Citation < ActiveRecord::Base
  belongs_to :publication
  belongs_to :reference, :class_name => "Publication"
end

class Article < Publication
end

class Book < Publication
end

class Chapter < Publication
end

现在我们可以创建数据库并从控制台试用：

$ rake db:migrate
$ script/console 
Loading development environment (Rails 2.2.2)
>> a = Article.create!(:name => "Article")
=> #<Article id: 1, ...>
>> b = Book.create!(:name => "Book")
=> #<Book id: 2, ...>
>> a.citations.create(:reference => b)
=> #<Citation id: 1, publication_id: 1, reference_id: 2, created_at: "2009-02-15 14:13:15", updated_at: "2009-02-15 14:13:15">
>> a.citations
=> [#<Citation id: 1, ...>]
>> a.references
=> []
>> b.citations
=> []
>> b.references
=> [#<Citation id: 1, publication_id: 1, reference_id: 2, created_at: "2009-02-15 14:13:15", updated_at: "2009-02-15 14:13:15">]    
>> a.cited_publications
=> [#<Book id: 2, type: "Book", name: "Book", created_at: "2009-02-15 14:11:00", updated_at: "2009-02-15 14:11:00">]
>> a.refered_publications
=> []
>> b.cited_publications
=> []
>> b.refered_publications
=> [#<Article id: 1, type: "Article", name: "Article", created_at: "2009-02-15 14:10:51", updated_at: "2009-02-15 14:10:51">]

Answer 2

这是一个不对发布使用单表继承的解决方案。这意味着有文章、书籍和章节表，而不是一个出版物表。以下是创建应用程序要运行的命令：

$ rails myproject
$ cd myproject
$ script/generate model book name:string
$ script/generate model chapter name:string
$ script/generate model article name:string
$ script/generate model citation publication_type:string publication_id:integer reference_type:string reference_id:integer

在lib/acts_as_publication.rb中创建这个文件：

module ActsAsPublication
  def self.included(base)
    base.extend(ClassMethods)
  end
  module ClassMethods
    def acts_as_publication
      has_many :citations, :as => :publication
      has_many :references, :as => :reference, :class_name => "Citation"      
    end
  end
end

在config/initializers/acts_as_publication.rb中创建这个文件：

ActiveRecord::Base.send(:include, ActsAsPublication)

然后在每个模型、文章、书籍和章节中调用它，如下所示：

class Article < ActiveRecord::Base
  acts_as_publication
end

然后在app/models/citation.rb中添加这些关系：

class Citation < ActiveRecord::Base
  belongs_to :publication, :polymorphic => true
  belongs_to :reference, :polymorphic => true
end

现在我们可以创建数据库并从控制台试用：

$ rake db:migrate
$ script/console 
Loading development environment (Rails 2.2.2)
>> a = Article.create!(:name => "a")
=> #<Article id: 1, ...>
>> b = Article.create!(:name => "b")
=> #<Article id: 2, ...>
>> Citation.create!(:publication => a, :reference => b)
=> #<Citation id: 1, publication_type: "Article", publication_id: 1, reference_type: "Article", reference_id: 2, created_at: "2009-02-15 13:14:27", updated_at: "2009-02-15 13:14:27">
>> a.citations
=> [#<Citation id: 1, ...>]
>> a.references
=> []
>> b.citations
=> []
>> b.references
=> [#<Citation id: 1, ...>]
>> Book.create!(:name => "foo")
=> #<Book id: 1, name: "foo", created_at: "2009-02-15 13:18:23", updated_at: "2009-02-15 13:18:23">
>> a.citations.create(:reference => Book.first)
=> #<Citation id: 2, publication_type: "Article", publication_id: 1, reference_type: "Book", reference_id: 1, created_at: "2009-02-15 13:18:52", updated_at: "2009-02-15 13:18:52">
>> Book.first.references
=> [#<Citation id: 2, ...>]
>> a.citations
=> [#<Citation id: 1, publication_type: "Article", publication_id: 1, reference_type: "Article", reference_id: 2, created_at: "2009-02-15 13:14:27", updated_at: "2009-02-15 13:14:27">, #<Citation id: 2, publication_type: "Article", publication_id: 1, reference_type: "Book", reference_id: 1, created_at: "2009-02-15 13:18:52", updated_at: "2009-02-15 13:18:52">]   

Answer 3

我在http://github.com/francois/so-536261/tree/master有一个不完整的答案

基本上，数据库架构确实支持您的用例，但 ActiveRecord 不支持。该解决方案可能会涉及使用 sql 查找或其他技巧。