Ruby on Rails中的多对多多态关联

Question

A Video,a Song和an Article可以有很多Tags.每个人Tag也可以有很多Video, Songs or Articles.所以我有5个型号:Video, Song, Article, Tag and Taggings.

以下是这些型号:

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

数据库的定义 Taggings

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

Taggings 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,我有正确的模型定义(belongs_to,has_many？)？我的直觉告诉我,我错过了一些东西.我看过很多文章,我很困惑.

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.

除了它的名字,你的课Taggings似乎没问题.它必须是单一的,:Tagging

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