Reindexing programmatically in Magento 2

m2_reindexall_programmatically.php

<?php

/**
 * @license http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
 * @author Hervé Guétin <herve.guetin@gmail.com> <@herveguetin>
 */
class Reindex
{
    /**
     * @var \Magento\Indexer\Console\Command\IndexerReindexCommand
     */
    private $reindexCommand;

    public function __construct(
        \Magento\Indexer\Console\Command\IndexerReindexCommand $reindexCommand
    )
    {
        $this->reindexCommand = $reindexCommand;
    }

    public function reindexAll()
    {
        $this->reindexCommand->run(
            new \Symfony\Component\Console\Input\StringInput('index'),
            new \Symfony\Component\Console\Output\ConsoleOutput()
        );
    }
}

I can't run reindexAll(), because of wrong instances... May you check https://magento.stackexchange.com/questions/174282/get-to-work-reindexing-in-external-code/ ?