bank_account.rb

class BankAccount < ActiveRecord::Base
  include AttributeEncryption

  belongs_to :billable, polymorphic: true
  encrypted_attribute :encrypted_number, hash: true

  validates :number,
    format: { with: /[pP]?\d*/ }

  # encrypted_attribute overrides #number= in order
  # to perform some encryption magic, hence a
  # before_validation hook does not work to strip
  # the account number from unwanted characters.
  alias_method :orig_number=, :number=
  def number=(value)
    value = value.gsub(/[ -\.]/, '') unless value.nil?
    send(:orig_number=, value)
  end
end