public function addDecorator($name, $seed)
    {
        if (!$this->columns[$name]) {
            throw new Exception(['No such column, cannot decorate', 'name' => $name]);
        }
        $decorator = $this->_add($this->factory($seed, ['table' => $this], 'TableColumn'));

        if (!is_array($this->columns[$name])) {
            $this->columns[$name] = [$this->columns[$name]];
        }
        $this->columns[$name][] = $decorator;

        return $decorator;
    }