Rails Active Record(Model) revierse polimorphic

It’s easy to do polymorphic associations in Ruby on Rails(Acitve Record):

• A Picture, a Video can belong to an Article
• A Picture can belong to either an Article

This example shows how to create an ArticleElement join model that handles the polymorphic relationship.

🐞 Model

class Article < ActiveRecord::Base
  has_many :article_elements
  has_many :pictures, through: :article_elements, source: :element, source_type: 'Picture', class_name: 'Picture'
  has_many :videos, through: :article_elements, source: :element, source_type: 'Video', class_name: 'Video'
end

class Picture < ActiveRecord::Base
  has_one :article_element, as: :element
  has_one :article, through: :article_elements
end

class Video < ActiveRecord::Base
  has_one :article_element, as: :element
  has_one :article, through: :article_elements 
end

class ArticleElement < ActiveRecord::Base
  belongs_to :article
  belongs_to :element, polymorphic: true
end

🏀 Migration

class CreateArticles < ActiveRecord::Migration[5.0]
  def change
    create_table :articles do |t|
      ...

      t.timestamps
    end
  end
end

class CreatePictures < ActiveRecord::Migration[5.0]
  def change
    create_table :pictures do |t|
      ...

      t.timestamps
    end
  end
end

class CreateVideos < ActiveRecord::Migration[5.0]
  def change
    create_table :videos do |t|
      ...

      t.timestamps
    end
  end
end

class CreateArticleElements < ActiveRecord::Migration[5.0]
  def change
    create_table :article_elements do |t|
      t.references :article, index: true
      t.references :element, polymorphic: true, index: true

      t.timestamps
    end
  end
end

🐝 Special Thanks

Reverse polymorphic associations in Rails

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