You are browsing the Symfony 4 documentation, which changes significantly from Symfony 3.x. If your app doesn't use Symfony 4 yet, browse the Symfony 3.4 documentation.

The Immutable Event Dispatcher

4.2 version

Maintained

3.4 4.3 4.3 master

Unmaintained

2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 3.0 3.1 3.2 3.3 4.0 4.1

edit this page

The Immutable Event Dispatcher¶

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 EventDispatcher dispatcher 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.