journalduhacker/app/models/invitation.rb

class Invitation < ActiveRecord::Base
  belongs_to :user

  validate do
    if !email.to_s.match(/\A[^@]+@[^@]+\.[^@]+\z/)
      errors.add(:email, "is not valid")
    end
  end

  before_create :create_code

  def create_code
    (1...10).each do |tries|
      if tries == 10
        raise "too many hash collisions"
      end

      if !Invitation.find_by_code(self.code = Utils.random_str(15))
        break
      end
    end
  end

  def send_email(root_url)
    InvitationMailer.invitation(root_url, self).deliver
  end
end