module.config.php

<?php

return array(
	// this doesn't seem to do anything
	'service_manager' => array(
		'invokables' => array(
			'Vendor\Validator\StartsWith' => 'Vendor\Validator\StartsWith',
		),
		'alias' => array(
			'StartsWith' => 'Vendor\Validator\StartsWith',
		),
	),
	// nor does this
	'validators' => array(
		'invokables' => array(
			'Vendor\Validator\StartsWith' => 'Vendor\Validator\StartsWith',
		),
		'alias' => array(
			'StartsWith' => 'Vendor\Validator\StartsWith',
		),
	),
);

MyForm.php

<?php

namespace Vendor\Form;

use Zend\Form\Form;
use Zend\Form\Element;
use Zend\Form\Annotation\InputFilter;
use Zend\InputFilter\InputFilterProviderInterface;

class MyForm extends Form implements InputFilterProviderInterface
{
	public function __construct(array $websites, $name = null)
	{
		parent::__construct($name);

		// ... elements
	}

	public function getInputFilterSpecification()
	{
		return array(
			'name' => array(
				'required' => true,
				'filters'  => array(
					array('name' => 'StripTags'),
					array('name' => 'StringTrim'),
				),
				'validators' => array(
					array(
						'name' => 'StartsWith', // works with Vendor\Validator\StartsWith
						'options' => array(
							'pattern' => '/^[a-z]/',
						),
					),
				),
			),
		);
	}
}

Output

Zend\ServiceManager\Exception\ServiceNotFoundException

File:
/home/tracked/vendor/zendframework/zendframework/library/Zend/ServiceManager/ServiceManager.php:496

Message:
Zend\Validator\ValidatorPluginManager::get was unable to fetch or create an instance for StartsWith

StartsWith.php

<?php

namespace Vendor\Validator;

use Zend\Validator\AbstractValidator;
use Traversable;
use Zend\Stdlib\ArrayUtils;

/**
 * Validator to check that the input starts with the specified pattern
 */
class StartsWith extends AbstractValidator
{
	const NO_MATCH = 'noMatch';

	/**
	 * Digits filter used for validation
	 *
	 * @var \Zend\Filter\Digits
	 */
	protected static $filter = null;

	/**
	 * Validation failure message template definitions
	 *
	 * @var array
	 */
	protected $messageTemplates = array(
		self::NO_MATCH => "This name must begin with a characters from the pattern '%pattern%'",
	);

	/**
	 * @var array
	 */
	protected $messageVariables = array(
		'pattern' => 'pattern'
	);

	/**
	 * The pattern to match against
	 *
	 * @var mixed
	 */
	protected $pattern;


	/**
	 * Sets validator options
	 *
	 * @param  array|Traversable $options
	 * @throws \InvalidArgumentException
	 */
	public function __construct($options = null)
	{
		if ($options instanceof Traversable)
		{
			$options = ArrayUtils::iteratorToArray($options);
		}

		if (!is_array($options))
		{
			$options = func_get_args();
			$temp['pattern'] = array_shift($options);

			$options = $temp;
		}

		if (!array_key_exists('pattern', $options) || is_null($options['pattern']))
		{
			throw new \InvalidArgumentException("Missing option 'pattern'");
		}

		$this->setPattern($options['pattern']);

		parent::__construct($options);
	}


	/**
	 * Returns the pattern
	 *
	 * @return string pattern
	 */
	public function getPattern()
	{
		return $this->pattern;
	}


	/**
	 * Sets the pattern
	 *
	 * @param string $pattern
	 * @return StartsWith Provides a fluent interface
	 */
	public function setPattern($pattern)
	{
		$this->pattern = $pattern;
		return $this;
	}


	/**
	 * Returns true if and only if $value only contains digit characters
	 *
	 * @param string $value
	 * @return bool
	 */
	public function isValid($value)
	{
		die("validator running!");
	}
}

The Problem

I can't seem to get Zend\Form to load my validator from the service manager. My ultimate goal is my validator is loaded from the service manager because I need to inject a dependency.

What is going wrong? What have I missed about this? What do I not understand? :(