Magento 2 Events List and How to Use Them

Table of contents

In this post we’re gonna show you how to use events in Magento 2. But first we need to understand about events and observers. The events and observers implementation in Magento 2 is based on the publish-subscribe pattern. Using events and observers, you can run your custom code in response to a specific Magento event or even a custom event.

What is events in Magento?

Events are dispatched by modules when certain actions are triggered. In addition to its own events, Magento allows you to create your own events that can be dispatched in your code. When an event is dispatched, it can pass data to any observers configured to watch that event.

What is observers in Magento?

Observers are a certain type of Magento class that can influence general behavior, performance, or change business logic. Observers are executed whenever the event they are configured to watch is dispatched by the event manager.

Now that we understand the terminologies, let’s put them into use!

1. Create event.xml file

You can create event.xml file for different areas:

Global area: app/code/Simi/HelloWorld/etc/events.xml
Frontend area: app/code/Simi/HelloWorld/etc/frontend/events.xml
Admin area: app/code/Simi/HelloWorld/etc/adminhtml/events.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="my_module_event_before">
        <observer name="myObserverName" instance="MyCompany\MyModule\Observer\MyObserver" />
    </event>
    <event name="my_module_event_after">
        <observer name="myObserverName" instance="MyCompany\MyModule\Observer\AnotherObserver" />
    </event>
</config>

2. Create Observer class

To create an observer, you must place your class file under your <module-root>/Observer directory. Your observer class should implement Magento\Framework\Event\ObserverInterface and define its execute function.

Below is an example of the basic observer class structure:

namespace MyCompany\MyModule\Observer;

use Magento\Framework\Event\ObserverInterface;

class MyObserver implements ObserverInterface
{
  public function __construct()
  {
    // Observer initialization code...
    // You can use dependency injection to get any class this observer may need.
  }

  public function execute(\Magento\Framework\Event\Observer $observer)
  {
    // Observer execution code...
  }
}

One of the powerful features of observers is that they are able to use parameters passed into the event when it was dispatched.

Here is an example of an observer obtaining data passed in when the event was dispatched:

namespace MyCompany\MyModule\Observer;

use Magento\Framework\Event\ObserverInterface;

class AnotherObserver implements ObserverInterface
{
  public function __construct()
  {
    // Observer initialization code...
    // You can use dependency injection to get any class this observer may need.
  }

  public function execute(\Magento\Framework\Event\Observer $observer)
  {
    $myEventData = $observer->getData('myEventData');
    // Additional observer execution code...
  }
}

Subscribing to events

Observers can be configured to watch certain events in the events.xml file.

The observer xml element has the following properties:

name (required) – The name of the observer for the event definition.
instance (required) – The fully qualified class name of the observer.
disabled – Determines whether this observer is active or not. Default value is false.
shared – Determines the lifestyle of the class. Default is true.

Below is an example of how to assign observers to watch certain events:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="my_module_event_before">
        <observer name="myObserverName" instance="MyCompany\MyModule\Observer\MyObserver" />
    </event>
    <event name="my_module_event_after">
        <observer name="myObserverName" instance="MyCompany\MyModule\Observer\AnotherObserver" />
    </event>
</config>

Note that observer names must be unique per event definition. You cannot have two observers with the same name in the same event definition to avoid an override.

3. Dispatch event

Events can be dispatched using the Magento\Framework\Event\Manager class. This class can be obtained through dependency injection by defining the dependency in your constructor.

To dispatch an event, call the dispatch function of the event manager class and provide it with the name of the event you want to dispatch along with an array of data you wish to provide to observers.

The following example shows you how to dispatch an event with and without an array of data.

namespace MyCompany\MyModule;

use Magento\Framework\Event\ManagerInterface as EventManager;

class MyClass
{
  /**
   * @var EventManager
   */
  private $eventManager;

  public function __construct(EventManager $eventManager)
  {
    $this->eventManager = $eventManager;
  }

  public function something()
  {
    $eventData = null;
    // Code...
    $this->eventManager->dispatch('my_module_event_before');
    // More code that sets $eventData...
    $this->eventManager->dispatch('my_module_event_after', ['myEventData' => $eventData]);
  }
}