polymorphic_many_to_many_in_rails.md

polymorphic_many_to_many_in_rails.md

Polymorphic many-to-many association in Rails

Migration

class CreateBannerCategories < ActiveRecord::Migration
  def change
    create_table :banner_categories do |t|
      t.integer :banner_id
      t.integer :category_id
      t.string :category_type

      t.timestamps
    end
  end
end

Models

class BannerCategory < ActiveRecord::Base
  belongs_to :category, polymorphic: true
  belongs_to :banner
  # fields are :category_id, :category_type, :banner_id
end

class Banner < ActiveRecord::Base
  has_many :provinces, through: :banner_categories, source: :category, source_type: "Province"
  has_many :countries, through: :banner_categories, source: :category, source_type: "Country"
  has_many :banner_categories, foreign_key: :banner_id
end

class Country < ActiveRecord::Base
  has_many :banners, through: :banner_categories, as: :category
  has_many :banner_categories, as: :category
end

class Province < ActiveRecord::Base
  has_many :banners, through: :banner_categories, as: :category
  has_many :banner_categories, as: :category
end

Sample

Province.first.banners
Country.first.banners

Banner.first.provinces
Country.first.provinces