find_subclass_by_slug.rb

class Provider
  include FindSubclassBySlug
end

module FindSubclassBySlug
  extend ActiveSupport::Concern

  class SubclassNotFound < StandardError; end

  included { load_subclasses! }

  class_methods do
    def namespace
      name.deconstantize.underscore
    end

    def slug
      name.demodulize.underscore
    end

    def find(slug)
      subclasses.find { |klass| klass.slug == slug }&.new
    end

    def find!(slug)
      find(slug) || raise(SubclassNotFound)
    end

    private

    def load_subclasses!
      Dir.glob("#{Rails.root}/app/models/#{namespace}/*.rb").each do |file|
        "#{namespace}/#{File.basename(file, '.rb')}".camelize.constantize
      end
    end
  end
end