# Class yii\base\Event

Inheritance | yii\base\Event » yii\base\BaseObject
Implements | yii\base\Configurable
Subclasses | yii\base\ActionEvent, yii\base\ModelEvent, yii\base\ViewEvent, yii\base\WidgetEvent, yii\db\AfterSaveEvent, yii\httpclient\RequestEvent, yii\i18n\MissingTranslationEvent, yii\mail\MailEvent, yii\web\UserEvent
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/base/Event.php

Event is the base class for all event classes.

It encapsulates the parameters associated with an event. The $sender property describes who raises the event. And the $handled property indicates if the event is handled. If an event handler sets $handled to be `true`, the rest of the uninvoked handlers will no longer be called to handle the event.

Additionally, when attaching an event handler, extra data may be passed and be available via the $data property when the event handler is invoked.

For more details and usage information on Event, see the guide article on events.

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$data | mixed | The data that is passed to yii\base\Component::on() when attaching an event handler. | yii\base\Event
$handled | boolean | Whether the event is handled. | yii\base\Event
$name | string | The event name. | yii\base\Event
$sender | object | The sender of this event. | yii\base\Event

## Public Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\BaseObject
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of an object property. | yii\base\BaseObject
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\BaseObject
__set() | Sets value of an object property. | yii\base\BaseObject
__unset() | Sets an object property to null. | yii\base\BaseObject
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\BaseObject
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\BaseObject
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
hasHandlers() | Returns a value indicating whether there is any handler attached to the specified class-level event. | yii\base\Event
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\BaseObject
hasProperty() | Returns a value indicating whether a property is defined. | yii\base\BaseObject
init() | Initializes the object. | yii\base\BaseObject
off() | Detaches an event handler from a class-level event. | yii\base\Event
offAll() | Detaches all registered class-level event handlers. | yii\base\Event
on() | Attaches an event handler to a class-level event. | yii\base\Event
trigger() | Triggers a class-level event. | yii\base\Event

## Property Details

$data public property

The data that is passed to yii\base\Component::on() when attaching an event handler. Note that this varies according to which event handler is currently executing.

public mixed $data = null
$handled public property

Whether the event is handled. Defaults to `false`. When a handler sets this to be `true`, the event processing will stop and ignore the rest of the uninvoked event handlers.

public boolean $handled = false
$name public property

The event name. This property is set by yii\base\Component::trigger() and trigger(). Event handlers may use this property to check what event it is handling.

public string $name = null
$sender public property

The sender of this event. If not set, this property will be set as the object whose `trigger()` method is called. This property may also be a `null` when this event is a class-level event which is triggered in a static context.

public object $sender = null

## Method Details

hasHandlers() public static method

Returns a value indicating whether there is any handler attached to the specified class-level event.

Note that this method will also check all parent classes to see if there is any handler attached to the named event.

public static boolean hasHandlers ( $class, $name )
$class | string|object | The object or the fully qualified class name specifying the class-level event.
$name | string | The event name.
return | boolean | Whether there is any handler attached to the event.

off() public static method

Detaches an event handler from a class-level event.

This method is the opposite of on().

Note: in case wildcard pattern is passed for class name or event name, only the handlers registered with this wildcard will be removed, while handlers registered with plain names matching this wildcard will remain.

See also on().

public static boolean off ( $class, $name, $handler = null )
$class | string | The fully qualified class name from which the event handler needs to be detached.
$name | string | The event name.
$handler | callable | The event handler to be removed. If it is `null`, all handlers attached to the named event will be removed.
return | boolean | Whether a handler is found and detached.

offAll() public static method (available since version 2.0.10)

Detaches all registered class-level event handlers.

See also:

- on()
- off()

public static void offAll ( )

on() public static method

Attaches an event handler to a class-level event.

When a class-level event is triggered, event handlers attached to that class and all parent classes will be invoked.

For example, the following code attaches an event handler to `ActiveRecord`'s `afterInsert` event:

    Event::on(ActiveRecord::className(), ActiveRecord::EVENT_AFTER_INSERT, function ($event) {
        Yii::trace(get_class($event->sender) . ' is inserted.');
    });

The handler will be invoked for EVERY successful ActiveRecord insertion.

Since 2.0.14 you can specify either class name or event name as a wildcard pattern:

    Event::on('app\models\db\*', '*Insert', function ($event) {
        Yii::trace(get_class($event->sender) . ' is inserted.');
    });

For more details about how to declare an event handler, please refer to yii\base\Component::on().

See also off().

public static void on ( $class, $name, $handler, $data = null, $append = true )
$class | string | The fully qualified class name to which the event handler needs to attach.
$name | string | The event name.
$handler | callable | The event handler.
$data | mixed | The data to be passed to the event handler when the event is triggered. When the event handler is invoked, this data can be accessed via yii\base\Event::$data.
$append | boolean | Whether to append new event handler to the end of the existing handler list. If `false`, the new handler will be inserted at the beginning of the existing handler list.

trigger() public static method

Triggers a class-level event.

This method will cause invocation of event handlers that are attached to the named event for the specified class and all its parent classes.

public static void trigger ( $class, $name, $event = null )
$class | string|object | The object or the fully qualified class name specifying the class-level event.
$name | string | The event name.
$event | yii\base\Event | The event parameter. If not set, a default yii\base\Event object will be created.