Thinking about how to model connecting a Group to a User

gistfile1.rb

class Hydramata::Connection
  include Virtus.model
  include ActiveModel::Validations
  extend ActiveModel::Naming

  attribute :current_user, User
  attribute :group_id, String
  attribute :user_id, String
  attribute :role, Sting

  validates :role, inclusion: { ['manager', 'editor', 'soon?']}

  def group
    @group ||= Group.find(group_id)
  end

  def user
    @user ||= User.find(user_id)
  end

  def save
    valid? ? persist : false
  end

  private
  def persist
    group.add_member(user) && user.add_group(group)
  end
end