Alias for_ delegated types in Rails 6.1

delegated_type.rb

# intended to be a Rails 6.1 initializer based on @rolandstuder's https://github.com/rails/rails/pull/41506
# if you want to use it with Rails 7, you will need to add a third options: parameter to the method
module ActiveRecord
  module DelegatedType
    private
    def define_delegated_type_methods(role, types:)
      role_type = "#{role}_type"
      role_id   = "#{role}_id"

      define_method "#{role}_class" do
        public_send("#{role}_type").constantize
      end

      define_method "#{role}_name" do
        public_send("#{role}_class").model_name.singular.inquiry
      end

      types.each do |type|
        scope_name = type.tableize.gsub("/", "_")
        aliased_scope_name = "for_#{scope_name}"
        singular   = scope_name.singularize
        query      = "#{singular}?"

        scope scope_name, -> { where(role_type => type) }

        define_singleton_method(aliased_scope_name, singleton_method(scope_name))

        define_method query do
          public_send(role_type) == type
        end

        define_method singular do
          public_send(role) if public_send(query)
        end

        define_method "#{singular}_id" do
          public_send(role_id) if public_send(query)
        end
      end
    end
  end
end