PolymorphicBelongsTo

A typed wrapper around Rails' polymorphic belongs_to that takes an explicit list of allowed target classes. Includes a Tapioca DSL compiler that uses those classes to generate Sorbet RBI signatures for the association's accessors.

Install the gem and add to the application's Gemfile by executing:

bundle add polymorphic_belongs_to

class Comment < ApplicationRecord
  include PolymorphicBelongsTo

  polymorphic_belongs_to :commentable, types: [Post, Photo]
end

Run bin/tapioca dsl to regenerate RBIs.

polymorphic_belongs_to(name, types:, validate_types: true, optional: nil, **options)

• name — The association name, e.g. :commentable.
• types: — An array of allowed target classes. Used both as the source of truth for the type-inclusion validator and by the Tapioca DSL compiler when generating RBIs.
• validate_types: — Controls the validation of the "type" field:
  • true: (Default) installs the validator with the list of allowed target classes: validates :"#{name}_type", inclusion: ...
  • false: Skips the type-inclusion validator
  • {...}: A Hash is passed straight through to validates ..., inclusion:, so you can override in:, supply a custom message:, etc.
• optional: — Forwarded to belongs_to, see Rails documentation. This also controls the type inclusion validator's allow_nil option.
• **options — Any remaining keyword arguments are forwarded to the underlying belongs_to(name, polymorphic: true, ...) call (e.g. inverse_of:, dependent:).

Note: validate_types: defaults to true. optional: defaults to belongs_to behavior, which depends on your Rails version.

# Disable the "type inclusion" validator
polymorphic_belongs_to :commentable, types: [Post, Photo], validate_types: false

# Customize the "type inclusion" validator
polymorphic_belongs_to :commentable,
  types: [Post, Photo],
  validate_types: { in: ["Post", "Photo", "Repost"], message: "..." }

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

The gem is available as open source under the terms of the MIT License.