Custom url validation for Rails3

url.rb

# -*- coding: utf-8 -*-
class UrlValidator < ::ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    begin
      uri = ::Addressable::URI.parse(value)
      unless ["http", "https", "ftp"].include?(uri.scheme)
        raise ::Addressable::URI::InvalidURIError
      end
    rescue ::Addressable::URI::InvalidURIError
      record.errors[attribute] << "Invalid URL"
    end
  end
end