ProvidesEvents.php

<?php
/**
 * Zend Framework (http://framework.zend.com/)
 *
 * @link      http://github.com/zendframework/zf2 for the canonical source repository
 * @copyright Copyright (c) 2005-2013 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd New BSD License
 */

namespace Zend\EventManager;

use Traversable;

/**
 * A trait for objects that provide events
 */
trait ProvidesEvents
{
    /**
     * @var EventManagerInterface
     */
    protected $events;

    /**
     * Set the event manager instance used by this context
     *
     * @param  EventManagerInterface $events
     * @return mixed
     */
    public function setEventManager(EventManagerInterface $events)
    {
        $identifiers = array(__CLASS__, get_class($this));
        if (isset($this->eventIdentifier)) {
            if ((is_string($this->eventIdentifier))
                || (is_array($this->eventIdentifier))
                || ($this->eventIdentifier instanceof Traversable)
            ) {
                $identifiers = array_unique(array_merge($identifiers, (array) $this->eventIdentifier));
            } elseif (is_object($this->eventIdentifier)) {
                $identifiers[] = $this->eventIdentifier;
            }
            // silently ignore invalid eventIdentifier types
        }
        $events->setIdentifiers($identifiers);
        $this->events = $events;
        if (method_exists($this, 'attachDefaultListeners')) {
            $this->attachDefaultListeners();
        }
        return $this;
    }

    /**
     * Retrieve the event manager
     *
     * Lazy-loads an EventManager instance if none registered.
     *
     * @return EventManagerInterface
     */
    public function getEventManager()
    {
        if (!$this->events instanceof EventManagerInterface) {
            $this->setEventManager(new EventManager());
        }
        return $this->events;
    }
}