WARNING: You are browsing the documentation for Symfony 2.2 which is not maintained anymore. Consider upgrading your projects to Symfony 4.2.

The Immutable Event Dispatcher

2.2 version

Maintained

3.4 4.2 current 4.3 master

Unmaintained

2.1 2.3 2.4 2.5 2.6 2.7 2.8 3.0 3.1 3.2 3.3 4.0 4.1

The Immutable Event Dispatcher¶

New in version 2.1: This feature was added in Symfony 2.1.

The ImmutableEventDispatcher is a locked or frozen event dispatcher. The dispatcher cannot register new listeners or subscribers.

The ImmutableEventDispatcher takes another event dispatcher with all the listeners and subscribers. The immutable dispatcher is just a proxy of this original dispatcher.

To use it, first create a normal dispatcher (EventDispatcher or ContainerAwareEventDispatcher) and register some listeners or subscribers:

use Symfony\Component\EventDispatcher\EventDispatcher;

$dispatcher = new EventDispatcher();
$dispatcher->addListener('foo.action', function ($event) {
    // ...
});

// ...

Now, inject that into an ImmutableEventDispatcher:

use Symfony\Component\EventDispatcher\ImmutableEventDispatcher;
// ...

$immutableDispatcher = new ImmutableEventDispatcher($dispatcher);

You'll need to use this new dispatcher in your project.

If you are trying to execute one of the methods which modifies the dispatcher (e.g. addListener), a BadMethodCallException is thrown.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.