Refactoring complex phone validations I have a complex phone validation that does the following:


First, check if either a home phone, mobile phone or work phone is provided (there will be 3 text fields in form and at least one type of phone number is required).
Strip out any characters from the phone number that is not a digit except 'x' and '+', since those represent extensions and are valid.
Make sure that the phones that were provided actually pass the phone number regex test.


And this is how I implemented the 3 steps above:

  VALID_PHONE_FORMAT = /\A(?:(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?\z/

  validate :phone_provided
  before_validation :clean_phone_numbers
  validates_format_of :phone_home, with: VALID_PHONE_FORMAT, if: :home_is_filled?
  validates_format_of :phone_mobile, with: VALID_PHONE_FORMAT, if: :mobile_is_filled?
  validates_format_of :phone_work, with: VALID_PHONE_FORMAT, if: :work_is_filled?
  validates_format_of :phone_fax, with: VALID_PHONE_FORMAT, if: :fax_is_filled?

 private

  def clean_phone_numbers
    if phone_home.present?
      self[:phone_home] = strip_bad_characters :phone_home
    end
    if phone_mobile.present?
      self[:phone_mobile] = strip_bad_characters :phone_mobile
    end
    if phone_work.present?
      self[:phone_work] = strip_bad_characters :phone_work
    end
    if phone_fax.present?
      self[:phone_fax] = strip_bad_characters :phone_fax
    end
  end

  def strip_bad_characters(attr)
    send("#{attr}_before_type_cast").gsub(/[^\d+!x]/,'')
  end

  def phone_provided
    if phone_home.blank? &amp;&amp; phone_mobile.blank? &amp;&amp; phone_work.blank?
      errors.add(:base, "Must provide a phone number")
    end
  end

  def home_is_filled?
    !phone_home.blank?
  end

  def mobile_is_filled?
    !phone_mobile.blank?
  end

  def work_is_filled?
    !phone_work.blank?
  end

  def fax_is_filled?
    !phone_fax.blank?
  end


I particularly don't like how I am calling 4 different methods in the if condition for validates_format_of. I would like to only use one method and be able to tell which attribute to call blank? on. How can I refactor this?
Let's summarize the business rules:


Characters other than digits, !, or x are stripped.
If any of the four types of phone numbers is provided, it must be valid.
At least one of { home, mobile, work } must be provided.


Requirement 3 is taken care of by validate :phone_provided, which is simple and fine.

The dissatisfaction comes from implementing Requirements 1 and 2.



The implementation of Requirement 1 can be simplified by making strip_bad_characters() tolerant of nil.  You can also call #read_attribute_before_type_cast() to avoid interpolation.

def strip_bad_characters(attr)
  input = read_attribute_before_type_cast(attr)
  input.gsub(/[^\d+!x]/, '') if input
end


Also, clean_phone_numbers() can use a loop:

def clean_phone_numbers
  [:phone_home, :phone_mobile, :phone_work, :phone_fax].each do |attr|
    self[attr] = strip_bad_characters(attr)
  end
end




The solution for Requirement 2 is simple: wrap the entire regular expression in \A( )?\Z to make it optional.  Then, you can get rid of all the …_is_filled? helpers.