Magento 2 Create Events - Observer in Magento 2

In this example we will should you How to create a event in Magento 2, we only catch the event to show the word Mageplaza - Event on the frontend so we should create an events.xml file in etc/frontend folder.

Overview of creating events in Magento 2

Step 1: Dispatch event
Step 2: Create a event file: events.xml
Step 3: Create Observer class
Step 4: Flush cache and check the result

Understand Catching and handling a event

Magento use area definition to manage the store. We will have a frontend area and admin area. With the configuration file, they can be put in 3 places:

Under etc/ folder is the configuration which can be used in both admin and frontend.
Under etc/frontend folder will be used for frontend area.
Under etc/adminhtml folder will be used for admin area.

The same with the event configuration file. You can create events configuration file for each area like this:

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

Step 1: Dispatch event

Now we want to dispatch an magento 2 event list which allow other module can change the word displayed. We will change the controller like this:

File: app/code/Mageplaza/HelloWorld/Controller/Index/Test.php

Content would be:

<?php

namespace Mageplaza\HelloWorld\Controller\Index;

class Test extends \Magento\Framework\App\Action\Action
{

	public function execute()
	{
		$textDisplay = new \Magento\Framework\DataObject(array('text' => 'Mageplaza'));
		$this->_eventManager->dispatch('mageplaza_helloworld_display_text', ['mp_text' => $textDisplay]);
		echo $textDisplay->getText();
		exit;
	}
}

The dispatch method will receive 2 arguments: an unique event name and an array data. In this example, we add the data object to the event and call it back to display the text.

Step 2: Create a event file: events.xml

File: app/code/Mageplaza/HelloWorld/etc/frontend/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="mageplaza_helloworld_display_text">
        <observer name="mp_display_text" instance="Mageplaza\HelloWorld\Observer\ChangeDisplayText" />
    </event>
</config>

In this file, under config element, we define an event element with the name is the event name which was dispatch above. The class which will execute this event will be define in the observer element by instance attribute. The name of observer is used to identify this with other observers of this event.

With this events.xml file, Magento will execute class Mageplaza\HelloWorld\Observer\ChangeDisplayText whenever the dispatch method of this event was called on frontend area. Please note that, we place events.xml in the frontend area, so if you dispatch that event in the admin area (like admin controller), it will not run.

Step 3: Create Observer class

Now we will create a class to execute above event.

File: app/code/Mageplaza/HelloWorld/Observer/ChangeDisplayText.php

<?php

namespace Mageplaza\HelloWorld\Observer;

class ChangeDisplayText implements \Magento\Framework\Event\ObserverInterface
{
	public function execute(\Magento\Framework\Event\Observer $observer)
	{
		$displayText = $observer->getData('mp_text');
		echo $displayText->getText() . " - Event </br>";
		$displayText->setText('Execute event successfully.');

		return $this;
	}
}

This class will implement the ObserverInterface and declare the execute method. You can see this simple method to know how it work.