Events
Events are used to communicate between different aspects of the Nextcloud eco system. They are used in the Nextcloud server internally, for server-to-apps communcation as well as inter-app communication.
Overview
The term “events” is a bit broad in Nextcloud and there are multiple ways of emitting them.
OCP event dispatcher
This mechanism is a versatile and typed approach to events in Nextcloud’s php code. It uses objects rather than just passing primitives or untyped arrays. This should help provide a better developer experience while lowering the risk of unexpected changes in the API that are hard to find after the initial implementation.
Naming scheme
The name should reflect the subject and the actions. Suffixing event classes with Event makes it easier to recognize their purpose.
For example, if a user is created, a UserCreatedEvent will be emitted.
Events are ususally evmitted after the event has happened. If it’s emitted before, it should be prefixed with Before.
Thus BeforeUserCreatedEvent is emitted before the user data is written to the database.
Note
Although you may chose to name your event classes differently, sticking to the convention will allow Nextcloud developers understand each other’s apps more easily.
Writing events
As a rule events are dedicated classes extending \OCP\EventDispatcher\Event.
<?php
use OCP\EventDispatcher\Event;
namespace OCA\MyApp\Event;
class AddEvent extends Event {}
The event above allows signalling that something happened. But in many cases you want to actually transport data like the affected resource with the event. Then the events act as simple data transfer objects. Therefore they need a constructor that takes the arguments, private members to store them and getters to access the values in listeners.
<?php
use OCP\EventDispatcher\Event;
use OCP\IUser;
class UserCreatedEvent extends Event {
/** @var IUser */
private $user;
public function __construct(IUser $user) {
parent::__construct();
$this->user = $user;
}
public function getUser(): IUser {
return $this->user;
}
}
Writing a listener
A listener can be a simple callback function (or anything else that is callable, or a dedicated class.
Listener callbacks
You can use simple callback to react on events. They will receive the event object as first and only parameter. You can type-hint the base Event class or the subclass you expect and register for.
<?php
use OCA\MyApp\Event\AddEvent;
use OCP\AppFramework\App;
use OCP\EventDispatcher\IEventDispatcher;
namespace OCA\MyApp\AppInfo;
class Application extends App {
public function __construct() {
parent::__construct('myapp');
/* @var IEventDispatcher $eventDispatcher */
$dispatcher = $this->getContainer()->query(IEventDispatcher::class);
$dispatcher->addListener(AddEvent::class, function(AddEvent $event) {
// ...
});
}
}
Note
Type-hinting the actual event class will give you better IDE and static analyzers support. It’s generally safe to assume the dispatcher will not give you any other objects.
Listener classes
A class that can handle an event will implement the \OCP\EventDispatcher\IEventListener interface. Class names should end with Listener.
<?php
use OCA\MyApp\Event\AddEvent;
use OCP\EventDispatcher\Event;
use OCP\EventDispatcher\IEventListener;
namespace OCA\MyApp\Event;
class AddTwoListener implements IEventListener {
public function handle(Event $event): void {
if (!($event instanceOf AddEvent)) {
return;
}
$event->addToCounter(2);
}
}
Note
Php parameter type hints are not allowed to be more specific than the type hints on the interface, thus you can’t use AddEvent in the method signature but use an instanceOf instead.
In the Application.php the event and the listener class are connected. The class is instantiated only when the actual event is fired.
<?php
use OCA\MyApp\Event\AddEvent;
use OCA\MyApp\Listener\AddTwoListener;
use OCP\AppFramework\App;
use OCP\EventDispatcher\IEventDispatcher;
namespace OCA\MyApp\AppInfo;
class Application extends App {
public function __construct() {
parent::__construct('myapp');
/* @var IEventDispatcher $eventDispatcher */
$dispatcher = $this->getContainer()->query(IEventDispatcher::class);
$dispatcher->addServiceListener(AddEvent::class, AddTwoListener::class);
}
}
Note
The listener is resolved via the DI container, therefore you can add a constructor and type-hint services required for processing the event.
Available Events
Here you find an overview of the public events that can be consumed in apps. See their source files for more details.
\OCA\Files\Event\LoadAdditionalScriptsEvent
Available in Nextcloud 17 and later.
This event is triggered when the files app is rendered. It canb e used to add additional scripts to the files app.
\OCA\Viewer\Event\LoadViewer
Available in Nextcloud 17 and later.
This event is triggered whenever the viewer is loaded and extensions should be loaded.
\OCP\Authentication\Events\LoginFailedEvent
Available in Nextcloud 19 and later.
Emitted when the authentication fails, but only if the login name can be associated with an existing user.
\OCP\Contacts\Events\ContactInteractedWithEvent
Available in Nextcloud 19 and later.
Event emitted by apps whenever there was an interaction with another user or contact.
It is an event that allows apps to notify other components about an interaction between two users. This can be used to build better recommendations and suggestions in user interfaces.
Emitters should add at least one identifier (uid, email, federated cloud ID) of the recipient of the interaction.
\OCP\DirectEditing\RegisterDirectEditorEvent
Available in Nextcloud 18 and later.
Event to allow to register the direct editor.
\OCP\Files\Events\BeforeFileScannedEvent
Available in Nextcloud 18 and later.
\OCP\Files\Events\BeforeFolderScannedEvent
Available in Nextcloud 18 and later.
\OCP\Files\Events\FileCacheUpdated
Available in Nextcloud 18 and later.
\OCP\Files\Events\FileScannedEvent
Available in Nextcloud 18 and later.
\OCP\Files\Events\FolderScannedEvent
Available in Nextcloud 18 and later.
\OCP\Files\Events\NodeAddedToCache
Available in Nextcloud 18 and later.
\OCP\Files\Events\NodeRemovedFromCache
Available in Nextcloud 18 and later.
\OCP\Group\Events\BeforeGroupCreatedEvent
Available in Nextcloud 18 and later.
\OCP\Group\Events\BeforeGroupDeletedEvent
Available in Nextcloud 18 and later.
\OCP\Group\Events\BeforeUserAddedEvent
Available in Nextcloud 18 and later.
\OCP\Group\Events\BeforeUserRemovedEvent
Available in Nextcloud 18 and later.
Deprecated in 20.0.0 - it can’t be guaranteed that this event is triggered in all case (e.g. for LDAP users this isn’t possible)
\OCP\Group\Events\GroupCreatedEvent
Available in Nextcloud 18 and later.
\OCP\Group\Events\GroupDeletedEvent
Available in Nextcloud 18 and later.
\OCP\Group\Events\UserAddedEvent
Available in Nextcloud 18 and later.
\OCP\Group\Events\UserRemovedEvent
Available in Nextcloud 18 and later.
\OCP\Mail\Events\BeforeMessageSent
Available in Nextcloud 19 and later.
Emitted before a system mail is sent. It can be used to alter the message.
\OCP\Security\CSP\AddContentSecurityPolicyEvent
Available in Nextcloud 17 and later.
Allows to inject something into the default content policy. This is for example useful when you’re injecting Javascript code into a view belonging to another controller and cannot modify its Content-Security-Policy itself. Note that the adjustment is only applied to applications that use AppFramework controllers.
WARNING: Using this API incorrectly may make the instance more insecure. Do think twice before adding whitelisting resources. Please do also note that it is not possible to use the disallowXYZ functions.
\OCP\Security\Events\GenerateSecurePasswordEvent
Available in Nextcloud 18 and later.
\OCP\Security\Events\ValidatePasswordPolicyEvent
Available in Nextcloud 18 and later.
\OCP\Security\FeaturePolicy\AddFeaturePolicyEvent
Available in Nextcloud 17 and later.
Event that allows to register a feature policy header to a request.
\OCP\User\Events\BeforePasswordUpdatedEvent
Available in Nextcloud 18 and later.
Emitted before the user password is updated.
\OCP\User\Events\PasswordUpdatedEvent
Available in Nextcloud 18 and later.
Emitted when the user password has been updated.
\OCP\User\Events\BeforeUserCreatedEvent
Available in Nextcloud 18 and later.
Emitted before a new user is created on the back-end.
\OCP\User\Events\UserCreatedEvent
Available in Nextcloud 18 and later.
Emitted when a new user has been created on the back-end.
\OCP\User\Events\BeforeUserDeletedEvent
Available in Nextcloud 18 and later.
\OCP\User\Events\UserDeletedEvent
Available in Nextcloud 18 and later.
\OCP\User\Events\BeforeUserLoggedInEvent
Available in Nextcloud 18 and later.
\OCP\User\Events\BeforeUserLoggedOutEvent
Available in Nextcloud 18 and later.
Emitted before a user is logged out.
\OCP\User\Events\CreateUserEvent
Available in Nextcloud 18 and later.
\OCP\User\Events\PostLoginEvent
Available in Nextcloud 18 and later.
\OCP\User\Events\UserChangedEvent
Available in Nextcloud 18 and later.
\OCP\User\Events\UserLoggedInEvent
Available in Nextcloud 18 and later.
\OCP\User\Events\UserLoggedOutEvent
Available in Nextcloud 18 and later.
Emitted when a user has been logged out successfully.
\OCP\WorkflowEngine\RegisterChecksEvent
Available in Nextcloud 18 and later.
\OCP\WorkflowEngine\RegisterEntitiesEvent
Available in Nextcloud 18 and later.
\OCP\WorkflowEngine\RegisterOperationsEvent
Available in Nextcloud 18 and later.
Symfony event dispatcher
Warning
Using the Symfony event dispatcher mechanism is discouraged. Use the OCP event dispatcher abstraction instead.
tbd
Hooks
Warning
The hooks mechanism is deprecated. Use the OCP event dispatcher instead.
Hooks are used to execute code before or after an event has occurred. This is for instance useful to run cleanup code after users, groups or files have been deleted. Hooks should be registered in the app.php:
<?php
namespace OCA\MyApp\AppInfo;
$app = new Application();
$app->getContainer()->query('UserHooks')->register();
The hook logic should be in a separate class that is being registered in the Container:
<?php
namespace OCA\MyApp\AppInfo;
use \OCP\AppFramework\App;
use \OCA\MyApp\Hooks\UserHooks;
class Application extends App {
public function __construct(array $urlParams=array()){
parent::__construct('myapp', $urlParams);
$container = $this->getContainer();
/**
* Controllers
*/
$container->registerService('UserHooks', function($c) {
return new UserHooks(
$c->query('ServerContainer')->getUserManager()
);
});
}
}
<?php
namespace OCA\MyApp\Hooks;
use OCP\IUserManager;
class UserHooks {
private $userManager;
public function __construct(IUserManager $userManager){
$this->userManager = $userManager;
}
public function register() {
$callback = function($user) {
// your code that executes before $user is deleted
};
$this->userManager->listen('\OC\User', 'preDelete', $callback);
}
}
Available hooks
The scope is the first parameter that is passed to the listen method, the second parameter is the method and the third one the callback that should be executed once the hook is being called, e.g.:
<?php
// listen on user predelete
$callback = function($user) {
// your code that executes before $user is deleted
};
$userManager->listen('\OC\User', 'preDelete', $callback);
Hooks can also be removed by using the removeListener method on the object:
<?php
// delete previous callback
$userManager->removeListener(null, null, $callback);
The following hooks are available:
Session
Injectable from the ServerContainer by calling the method getUserSession().
Hooks available in scope \OC\User:
preSetPassword (\OC\User\User $user, string $password, string $recoverPassword)
postSetPassword (\OC\User\User $user, string $password, string $recoverPassword)
changeUser (\OC\User\User $user, string $feature, string $value)
preDelete (\OC\User\User $user)
postDelete (\OC\User\User $user)
preCreateUser (string $uid, string $password)
postCreateUser (\OC\User\User $user)
preLogin (string $user, string $password)
postLogin (\OC\User\User $user, string $password)
logout ()
UserManager
Injectable from the ServerContainer by calling the method getUserManager().
Hooks available in scope \OC\User:
preSetPassword (\OC\User\User $user, string $password, string $recoverPassword)
postSetPassword (\OC\User\User $user, string $password, string $recoverPassword)
preDelete (\OC\User\User $user)
postDelete (\OC\User\User $user)
preCreateUser (string $uid, string $password)
postCreateUser (\OC\User\User $user, string $password)
GroupManager
Hooks available in scope \OC\Group:
preAddUser (\OC\Group\Group $group, \OC\User\User $user)
postAddUser (\OC\Group\Group $group, \OC\User\User $user)
preRemoveUser (\OC\Group\Group $group, \OC\User\User $user)
postRemoveUser (\OC\Group\Group $group, \OC\User\User $user)
preDelete (\OC\Group\Group $group)
postDelete (\OC\Group\Group $group)
preCreate (string $groupId)
postCreate (\OC\Group\Group $group)
Filesystem root
Injectable from the ServerContainer by calling the method getRootFolder(), getUserFolder() or getAppFolder().
To enable these events for your app you should add the following to your info.xml file:
<types>
<filesystem/>
</types>
Filesystem hooks available in scope \OC\Files:
preWrite (\OCP\Files\Node $node)
postWrite (\OCP\Files\Node $node)
preCreate (\OCP\Files\Node $node)
postCreate (\OCP\Files\Node $node)
preDelete (\OCP\Files\Node $node)
postDelete (\OCP\Files\Node $node)
preTouch (\OCP\Files\Node $node, int $mtime)
postTouch (\OCP\Files\Node $node)
preCopy (\OCP\Files\Node $source, \OCP\Files\Node $target)
postCopy (\OCP\Files\Node $source, \OCP\Files\Node $target)
preRename (\OCP\Files\Node $source, \OCP\Files\Node $target)
postRename (\OCP\Files\Node $source, \OCP\Files\Node $target)
Filesystem scanner
Filesystem scanner hooks available in scope \OC\Files\Utils\Scanner:
scanFile (string $absolutePath)
scanFolder (string $absolutePath)
postScanFile (string $absolutePath)
postScanFolder (string $absolutePath)
Public emitter
Warning
The public emitter mechanism is deprecated. Use the OCP event dispatcher instead.
tbd