CODEWITHSUNDEEP
ruby-on-railsrubyactiverecordruby-on-rails-3.2database-schema
user266003
user266003

Reputation:

Many to many polymorphic association in Ruby on Rails

A Video, a Song and an Article can have many Tags. And each Tag also can have many Video, Songs or Articles. So I have 5 models: Video, Song, Article, Tag and Taggings.

Here are these models:

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

The database definition of 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 model:

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

The issue I'm worried by is, do I have right definitions of model (belongs_to, has_many?) ? My gut tells me that I missed something. I've seen many articles and I'm quite confused by them.

Upvotes: 4

Views: 2010

Answers (1)

jdoe
jdoe

Reputation: 15771

You need these changes:

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

About with_options.

Your class Taggings seems ok except its name. It has to be singular, Tagging:

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

Upvotes: 10

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