ruby-on-rails - Ruby on Rails 中的多对多多态关联

Question

Video、Song 和Article 可以有很多标签。每个标签也可以有很多视频、歌曲或文章。所以我有 5 个模型:Video、Song、Article、Tag 和 Taggings。

这是这些模型:

class Video < ActiveRecord::Base
  has_many :tags, :through => :taggings
end

class Song < ActiveRecord::Base
  has_many :tags, :through => :taggings
end

class Article < ActiveRecord::Base
  has_many :tags, :through => :taggings
end

class Tag < ActiveRecord::Base
  has_many :articles
  has_many :videos
  has_many :songs
  belong_to :taggings, :polymorphic => true #is this correct?
end

Taggings 的数据库定义

create_table "taggings", :force => true do |t|
  t.integer  "tag_id"
  t.string   "taggable_type"
  t.integer  "taggable_id"
  t.datetime "created_at",    :null => false
  t.datetime "updated_at",    :null => false
end

标签模型:

class Taggings < ActiveRecord::Base
  belongs_to :tag                           #is this correct?
  belong_to :taggable, :polymorphic => true #is this correct?
end

我担心的问题是，我是否正确定义了模型(belongs_to、has_many？)？我的直觉告诉我，我错过了什么。我看过很多文章，但我对它们很困惑。

Answer 1

您需要这些更改:

class Video < ActiveRecord::Base # or Song, or Article
  has_many :taggings, :as => :taggable  # add this      
  has_many :tags, :through => :taggings # ok


class Tag < ActiveRecord::Base
  # WRONG! Tag has no tagging_id
  # belong_to :taggings, :polymorphic => true

  has_many :taggings # make it this way

  # WRONG! Articles are available through taggings
  # has_many :articles

  # make it this way
  with_options :through => :taggings, :source => :taggable do |tag|
    tag.has_many :articles, :source_type => 'Article'
    # same for videos
    # and for songs
  end

关于with_options .

你的类 Taggings 似乎没问题除了它的名字。它必须是单数，标记:

class Tagging < ActiveRecord::Base # no 's'!
  belongs_to :tag                           
  belong_to :taggable, :polymorphic => true 
end