My understanding of polymorphic associations is you have a an id column and a type column (which must be a model name):
attachable_id [Integer]
attachable_type [String]
class Asset < ActiveRecord::Base belongs_to :attachable, polymorphic: true end
class Post < ActiveRecord::Base has_many :assets, as: :attachable end
``
While this is nice in terms of simplicity, it can be somewhat limiting.
I would like the option to have my type column be an id pointing to another model, that could have the class name as column there:
attachable_id [Integer]
attachable_type_id [Integer]
class Asset < ActiveRecord::Base belongs_to :attachable_type belongs_to :attachable, polymorphic: true end
class Post < ActiveRecord::Base has_many :assets, as: :attachable end
model_name [String]
class AttachableType < ActiveRecord::Base end
``
The advantages for me are:
- Model name changes only need to happen in one place in the db
- The ability to add a foreign key constraint on type column
- Use up less space with an integer column instead of a text one I’m currently working on a moderately large Rails app that uses a lot of single-table inheritance, and am looking to replace it with polymorphism.
While I can do that with the existing functionality, abstracting my list of types into its own table (with extra metadata) would add a lot of convenience.
Please let me know if this sounds reasonable.
