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https://github.com/contao-community-alliance/event-dispatcher
Event dispatcher for Contao Open Source CMS
https://github.com/contao-community-alliance/event-dispatcher
Last synced: about 2 months ago
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Event dispatcher for Contao Open Source CMS
- Host: GitHub
- URL: https://github.com/contao-community-alliance/event-dispatcher
- Owner: contao-community-alliance
- License: lgpl-3.0
- Created: 2013-06-28T14:44:25.000Z (over 11 years ago)
- Default Branch: master
- Last Pushed: 2022-09-18T21:43:38.000Z (over 2 years ago)
- Last Synced: 2024-11-10T18:48:31.304Z (2 months ago)
- Language: PHP
- Homepage:
- Size: 125 KB
- Stars: 2
- Watchers: 9
- Forks: 3
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- Contributing: .github/CONTRIBUTING.md
- License: LICENSE
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README
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***NOTE:*** This is obsolete in Contao 4 - you should use the event dispatcher from the symfony kernel directly for
Contao 4 only extensions.
See below for maintaining compatibility with both Contao versions.
# Event dispatcher for Contao Open Source CMS
Why an event dispatcher for Contao Open Source CMS, are the hooks not enough?
First you need to understand, there is no real difference between hooks and events.
The are both notifications from within the system.
But events are more elastic than hooks. They can be hand round, consumed, stopped or bubble upon a hierarchy.
The real big reasons, why an event dispatcher exists for Contao are:
1. [Events](http://en.wikipedia.org/wiki/Event_%28computing%29) are standard paradigm in software design.
2. [Hooking](http://en.wikipedia.org/wiki/Hooking) is a paradigm to alter the behavior of a software, is it not designed for notifications.
3. Hooks are only a special form of events.
4. The [symfony event dispatcher](https://github.com/symfony/EventDispatcher) this extension based on is widely used.
5. The event dispatcher can handle every form of callbacks, like closures or static methods.
## Listen on events
The event dispatcher provide two ways to listen on events.
First and mostly used is an event listener. It is designed to listen on a single event.
Second the event subscriber is designed to listen on multiple events.
### Event listener per configuration
Since version 1.3 there are two ways to define your listeners per configuration.
#### /config/event_listeners.php
**We recommend to use this method!**
The file `/config/event_listeners.php` must return an array of event names as keys and listeners as values.
```php
array(
function($event) {
// event code
}
),
// With a static callable
'event-name' => array(
array('MyEventListener', 'myCallable')
),
// With an object callable
'event-name' => array(
array(new MyEventListener(), 'myCallable')
),
// With a service object
'event-name' => array(
array($GLOBALS['container']['my_event_listener'], 'myCallable')
),
// You can wrap the listener into an array with a priority
'event-name' => array(
array($listener, $priority)
),
);
```
#### /config/config.php
In your `/config/config.php` use `$GLOBALS['TL_EVENTS']` to register your event handlers.
With a closure:
```php
$GLOBALS['TL_EVENTS']['event-name'][] = function($event) {
// event code
};
```
With a static callable:
```php
$GLOBALS['TL_EVENTS']['event-name'][] = array('MyEventListener', 'myCallable');
```
With an object callable:
```php
$GLOBALS['TL_EVENTS']['event-name'][] = array(new MyEventListener(), 'myCallable');
```
#### Handle with priority
To define the priority, you can use an array with the listener as first and the priority as second element.
```php
$GLOBALS['TL_EVENTS']['event-name'][] = array($listener, $priority);
```
### Event listener per code
```php
$container['event-dispatcher']->addListener('event-name', $listener);
```
### Event subscriber per configuration
Since version 1.3 there are two ways to define your listeners per configuration.
#### /config/event_subscribers.php
**We recommend to use this method!**
The file `/config/event_subscribers.php` must return an array of subscribers.
```php
addSubscriber(new MyEventSubscriber());
```
## Compatibility with Contao 3 & 4.
You are encouraged to register your events directly in the symfony event dispatcher in Contao 4 using service
configuration files (yaml, xml, ...).
However, for maintaining compatibility, you still need to supply the `event_listeners.php` and `event_subscribers.php`
files as otherwise the events will not get registered in Contao 3.
To register events only in Contao 3, we suggest to return an empty array if the version compare is equal to 4.
```diff
=')) {
+ return [];
+ }
return [
'some.event' => ['Some\EventListener', 'someMethod']
];
```