composed model example

composed_model.rb

concern :ComposedModel do
  include ActiveModel::Model

  def valid?
    objects.all?(&:valid?) && super
  end

  def save!
    raise ActiveRecord::RecordInvalid, self unless valid?
    transaction { objects.each &:save! }
  end

  private

  delegate :transaction, to: ApplicationRecord, private: true

  def merge_errors_for! object, from:, to:
    object.errors.where(from).each { errors.import _1, attribute: to }
  end
end

registration.rb

class Space::Registration
  include ComposedModel

  attr_accessor *%i[space_name owner_name email]
  
  def valid?
    super
  ensure
    merge_errors!
  end
  
  private
  
  def objects = [space, owner, auth]
  
  def merge_errors!
    merge_errors_for! space, from: :name, to: :space_name
    merge_errors_for! owner, from: :name, to: :owner_name
    merge_errors_for! auth, from: :identifier, to: :email
  end

  memoize def space = ....
  memoize def owner = ....
  memoize def auth = ...
end