protected function getRequiredType(callable $callback)
	{
		$ref = new \ReflectionFunction($callback);
		
		if($ref->getNumberOfParameters() > 0)
		{
			$params = $ref->getParameters();
			
			if(isset($params[0]) &&  NULL !== ($type = $params[0]->getClass()))
			{
				return $type;
			}
		}
	}