uri_validator.rb

require 'uri'

class UriValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    if value.present?
      begin
        unless URI(value).is_a?(URI::HTTP)
          record.errors.add(attribute, :invalid_uri, options)
        end
      rescue
        record.errors.add(attribute, :invalid_uri, options)
      end
    end
  end
end