public function validatesFormatOf($attrs)
	{
		$configuration = array_merge(self::$DEFAULT_VALIDATION_OPTIONS, array('message' => Errors::$DEFAULT_ERROR_MESSAGES['invalid'], 'on' => 'save', 'with' => null));

		foreach ($attrs as $attr)
		{
			$options = array_merge($configuration, $attr);
			$attribute = $options[0];
			$var = $this->model->$attribute;

			if (is_null($options['with']) || !is_string($options['with']) || !is_string($options['with']))
				throw new ValidationsArgumentError('A regular expression must be supplied as the [with] option of the configuration array.');
			else
				$expression = $options['with'];

			if ($this->isNullWithOption($var, $options) || $this->isBlankWithOption($var, $options))
				continue;

			if (!@preg_match($expression, $var))
			$this->record->add($attribute, $options['message']);
		}
	}