棘手的活跃记录关系 - 多态双向自我指涉

Question

您如何模拟出版物(文章,书籍,章节等)的引用和引用？

出版物可以是文章,书籍或章节,它有许多参考其他出版物和其他出版物参考它(称这些引用)

我需要能够列出出版物之间的关系:出版物中的参考文献以及其他出版物对本出版物的引用

我最初的理解是,这将是处理不同类型的出版物的多态关系,并且它需要双向自联接.

我刺伤了它

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

我发现这有点令人困惑,所以任何有助于澄清它的建议都会很棒.甚至是对象和字段命名建议.

[我在这里问了一个不太清楚的问题.]

我也可能需要使用很多通过因为我需要能够破坏关系

Answer 1

这是使用单表继承使用自引用关系的解决方案.使用以下命令创建应用程序:

$ 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中试用它:

$ 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.以下是运行以创建应用程序的命令:

$ 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

创建此文件lib/acts_as_publication.rb:

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

创建此文件config/initializers/acts_as_publication.rb:

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

然后在每个模型,文章,书和章中调用,如下所示:

class Article < ActiveRecord::Base
  acts_as_publication
end

然后将这些关系添加到app/models/citation.rb:

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中试用它:

$ 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">]