gist.php

<?php
protected function interact(InputInterface $input, OutputInterface $output)
{
    $dialog    = $this->getDialogHelper();

    $inputValue = $dialog->askAndValidate($output, 'Enter some input: ', array($this, 'validateInput'));
}

public function validateInput($value)
{
    $validator = Validation::createValidator();
    $errors = $validator->validateValue($value, new Assert\NotBlank());
    if (count($errors)) {
        throw new \InvalidArgumentException((string) $errors);
    }

    return $value;
}