When you interact with the Public API, and with the content Repository i= n particular, Signals may be sent out, allowing you to rea= ct on actions triggered by the Repository. Those signals can be received by= dedicated services called Slots.
To learn more about SignalSlot in eZ Platform, please refer to the = dedicated documentation page.
This recipe will describe how to register a Slot for a dedicated Signal.=
As described in the SignalSlot documentation, a Slot is roughly like an event =
listener and must extend eZ\Publish\Core\SignalSlot\Slot.=
A typical implementation is the following:
namespace Acme\TestBundle\Slot;
use eZ\Publish\Core\SignalSlot\Slot as BaseSlot;
use eZ\Publish\Core\SignalSlot\Signal;
use eZ\Publish\API\Repository\ContentService;
=20
class OnPublishSlot extends BaseSlot
{
/**
* @var \eZ\Publish\API\Repository\ContentService
*/
private $contentService;
public function __construct( ContentService $contentService )
{
$this->contentService =3D $contentService;
}
=20
public function receive( Signal $signal )
{
if ( !$signal instanceof Signal\ContentService\PublishVersionSignal=
)
{
return;
}
// Load published content
$content =3D $this->contentService->loadContent( $signal->=
contentId, null, $signal->versionNo );
// Do stuff with it...
}
}=20
OnPublishSlot now needs to be registered as a service in th=
e ServiceContainer and identified as a valid Slot:
parameters:
my.onpublish_slot.class: Acme\TestBundle\Slot\OnPublishSlot
services:
my.onpublish_slot:
class: %my.onpublish_slot.class%
arguments: [@ezpublish.api.service.content]
tags:
- { name: ezpublish.api.slot, signal: ContentService\PublishVer=
sionSignal }=20
Service tag ezpublish.api.slot identifies =
your service as a valid Slot. The signal part (mandatory) says that this sl=
ot is listening to ContentService\PublishVersionSignal=
(shortcut for \eZ\Publish\Core\SignalSlot\Signal\ContentSer=
vice\PublishVersionSignal).
Internal signals emitted by Repository services are always relative to <= code>eZ\Publish\Core\SignalSlot\Signal namespace.
Hence ContentService\PublishVersionSignal means eZ\Pu=
blish\Core\SignalSlot\Signal\ContentService\PublishVersionSignal.
You can register a slot for any kind of signal by setting signal to * in the service tag.
eZ Platform comes with a generic slot that converts signals (including o= nes defined by user code) to regular event objects and exposes them via the= EventDispatcher. This makes it possible to implement a simple event listen= er/subscriber if you're more comfortable with this approach.
All you need to do is to implement an event listener or subscriber and r= egister it.
This very simple example will just log the received signal.
parameters:
my.signal_listener.class: Acme\TestBundle\EventListener\SignalListener
services:
my.signal_listener:
class: %my.signal_listener.class%
arguments: [@logger]
tags:
- { name: kernel.event_subscriber }=20
<?php
namespace Acme\TestBundle\EventListener;
use eZ\Publish\Core\MVC\Symfony\Event\SignalEvent;
use eZ\Publish\Core\MVC\Symfony\MVCEvents;
use Psr\Log\LoggerInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
class SignalListener implements EventSubscriberInterface
{
/**
* @var \Psr\Log\LoggerInterface
*/
private $logger;
public function __construct( LoggerInterface $logger )
{
$this->logger =3D $logger;
}
public function onAPISignal( SignalEvent $event )
{
$signal =3D $event->getSignal();
// You may want to check the signal type here to react accordingly
$this->logger->debug( 'Received Signal: ' . print_r( $signal,=
true ) );
}
public static function getSubscribedEvents()
{
return array(
MVCEvents::API_SIGNAL =3D> 'onAPISignal'
);
}
}=20