Magento Events & Observers

In the first place, to extend Magento functionality, we found people use Magento events and observers. Based on the publish-subscribe pattern Magento events and observers perform. Furthermore, you can run custom code for a specific Magento event by using Magento events and observers.

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Magento Events

When certain actions are processed Magento events are dispatched by modules. You can create your own Magento event with the help of Magento that can be dispatched in your code. Moreover, the data can be passed to any observers which are configured to watch the event when a Magento event is dispatched.

Magento Events Dispatching

By using,Magento>Framework>Event&gt Manager class the Magento events can be dispatched. Hence in your constructor by defining the dependency, this class can be obtained through dependency injection.

In fact, for dispatching a Magento event, you have to provide the name of the event you want to dispatch. Also, you need to call the dispatch function of the event manager class alongside an array of data, you want to provide the observers.

Below is an example provided where you can dispatch a Magento event with and without an array of data.

Creating New Magento Events

When you call the dispatch function, simply pass in a unique event name to the event manager in that way you can dispatch custom Magento events. Also, you can specify which observers will react to that Magento event in your module’s events.xml file.

Magento Events Area

Under the <module-root>/etc directory you’ll find the events.xml file. Generally, these events will be watched globally by the observers that are associated with the Magento events. To configure observers to be able to watch only the Magento events in specific areas the events.xml file needs to be defined under the module-root>etc/frontendand  module-root>etc/adminhtml directories.

Observers

If you want to influence the general behavior, performance, or change business logic then you can use observers which are a type of Magento class. Whenever the event as they are configured to watch is dispatched by the event manager, observers are executed.

Creating an Observer

In the first place under your module-root>/observer directory, you have to create an observer. For defining its execution of function your observer class should implement. Magento/Framework/Event/ ObserverInterface

Below we have provided an example of the basic observer class structure:

Furthermore, the most special feature of the observer is when event dispatched, it ables parameters to pass through the events. Following is an example of an event dispatched and the observer passed the data through events.

Magento Events Subscription

To watch certain Magento events in the events.xml file the observers can be configured. Following are the list of properties of an observer XML element:

Name(must) – For the Magento event definition it is the name of an observer.
Instance(must) – Class name of the observer must be fully qualified.
Disabled – It checks activeness that the observer is active or inactive.
Shared – Lifestyle of the class is determined and the default value is not TRUE.

Below you can see how you can assign observers to watch certain events:

In the above example, we denote the observer MyObserver to the custom event my_module_event_before and the other Observer as  my_module_event_after.

In Conclusion, per event definition, the observer names must be unique. As a result in the same event definition, you cannot have two observers with the same name. For example – both observers have the name.myObserverName It is possible because as the observers come from different event definitions.

Read the Magento official documentation for further information on Magento Events & Observers.