Registration of user and account: the Registrar model, shepherding the registration process

registrar.rb

# see https://gist.github.com/RichardJordan/9059633 for explanation
# -----------------------------------------------------------------

require_relative '../../lib/abilities/roles_admin'

class Registrar < Struct.new(:listener)

  attr_writer :admin_user_source, :registration_source, :responsibilities

  delegate :account, :fullname, :shortname, :email, :password,
            :password_confirmation, :user,   to: :registration

  def register(registration)
    @registration = registration

    if registration.valid?
      complete_registration

    else
      listener.create_registration_failed(registration)
    end
  end

  private

  def admin_user_source
    @admin_user_source ||= CustomerSupportUser.public_method(:new)
  end

  def build_account; end

  def build_user; end

  def complete_registration
    build_account
    build_user

    persist!

    listener.create_registration_succeeded(registration)
  end

  def grant_role
    roles_admin.grant_role!("owner", on_account: account, to_user: user)
  end

  def persist!
     grant_role if registration.save!
  end

  def registration
    @registration ||= registration_source.call
  end

  def registration_source
    @registration_source ||= Registration.public_method(:new)
  end

  def responsibilities
    @responsibilities ||= RolesAdmin
  end

  def roles_admin
    @roles_admin ||= admin_user_source.call.extend(responsibilities)
  end
end