url_validator.rb

class UrlValidator < ActiveModel::EachValidator

  # Credits to Lee Machin https://coderwall.com/p/ztig5g
  # Place this in app/validators/url_validator.rb

  def validate_each(record, attribute, value)
    record.errors[attribute] << (options[:message] || I18n.t(:must_be_valid_url)) unless url_valid?(value)
  end

  def url_valid?(url)
    self.class.url_valid?(url)
  end

  # A URL may be technically well-formed but may
  # not actually be valid, so this checks for both.
  # Use in models like:
  # UrlValidator.url_valid?("foo")
  # => false
  def self.url_valid?(url)
    url = URI.parse(url) rescue false
    url.kind_of?(URI::HTTP) || url.kind_of?(URI::HTTPS)
  end
end