...
Those two conditions allow the asynchronous processing of Slots. That means: It is possible to determine, by configuration, that a Slot must not receive a Signal in the very same moment it occurs, but to receive it on a later point in time, maybe after other Signals from a queue have been processed or even on a completely different server.
Signal
A Signal represents a specific event, e.g. that a content version has been published. It consists of information that is significant to the event, e.g. the content ID and version number. Therefore, a Signal is represented by an object of a class that is specific to the Signal and that extends from eZ\Publish\Core\SignalSlot\Signal. The full qualified name of the Signal class is used to uniquely identify the Signal. For example, the class eZ\Publish\Core\SignalSlot\Signal\ContentService\PublishVersionSignal identifies the example Signal.
...
| Info | ||
|---|---|---|
| ||
Signals can theoretically be sent by any object that gets hold of a SignalDispatcher (eZ\Publish\Core\SignalSlot\SignalDispatcher). However, at a first stage, Signals are only sent by special implementations of the Public API to indicate core events. These services must and will be used by default and will wrap the original service implementations. |
Slot
A Slot extends the system by realizing functionality that is executed when a certain Signal occurs. To implement a Slot, you must create a class that derives from eZ\Publish\Core\SignalSlot\Slot. The full qualified name of the Slot class is also used as the unique identifier of the Slot. The Slot base class requires you to implement the single method receive(). When your Slot is configured to listen to a certain Signal and this Signal occurs, the receive() method of your Slot is called.
...
Important: A single Slot should not take care of processing more than one Signal. Instead, if you need to trigger same or similar actions as different Signals occur. you should encapsulate these actions into a dedicated class, of which your Slots receive an instance to trigger this action.
Example: Updating URL aliases
Updating URL aliases is a typical process that can be realized through a Signal-Slot extension for different reasons:
...
| Info |
|---|
In order to make the newly created Slot react on the corresponding Signal, the following steps must be performed:
See How to listen to Core events recipe in the developer cookbook for more information. |