Refactoring complex phone validations

I have a complex phone validation that does the following:

1. 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).

2. Strip out any characters from the phone number that is not a digit except ‘x’ and ‘+’, since those represent extensions and are valid.

3. 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(?:(?:+?1s*(?:[.-]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? && phone_mobile.blank? && 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:

1. Characters other than digits, !, or x are stripped.
2. If any of the four types of phone numbers is provided, it must be valid.
3. 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.

You could do something like, using a little array magic

def clean_phone_numbers
  %w(phone_home phone_mobile phone_work phone_fax).each do |attribute|
    self[attribute.to_sym] = strip_bad_characters(attribute) if send(attribute).present?
  end
end

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