public function addFilterText($key, $name, $columns = null)
	{
		$columns = $columns === null? [$key] : (is_string($columns) ? [$columns] : $columns);

		if (!is_array($columns)) {
			throw new DataGridException('Filter Text can accept only array or string.');
		}

		$this->addFilterCheck($key);

		return $this->filters[$key] = new Filter\FilterText($this, $key, $name, $columns);
	}