---
schema_version: "1"
id: 48df85641771dbdc20e6e9fac43ec82c458ad05a13b5951b68dc7c1ae367ee88
title: Application Event Example
collection: developer
version: current
locale: en-us
portal_url: https://docs.salesforce.com/developer/current/en-us/platform/aura-platform/guides/aura/events/events-application-example.md
canonical_url: https://developer.salesforce.com/docs/platform/aura-platform/guide/events-application-example.html
source_site: developer.salesforce.com
content_type: documentation
content_hash: 88d8319118fcaafc216e015898b506dfb9f437cb91a65f722d0910894786bdd6
products:
  - Lightning Aura Components Developer Guide
  - Platform Developer Content
---

# Application Event Example

Here’s a simple use case of using an application event to update an attribute in another component.

1.  A user clicks a button in the notifier component, `aeNotifier.cmp`.
2.  The client-side controller for `aeNotifier.cmp` sets a message in a component event and fires the event.
3.  The handler component, `aeHandler.cmp`, handles the fired event.
4.  The client-side controller for `aeHandler.cmp` sets an attribute in `aeHandler.cmp` based on the data sent in the event.

**note:** The event and components in this example use the default `c` namespace. If your org has a namespace, use that namespace instead.

## Application Event

The `aeEvent.evt` application event has one attribute. We’ll use this attribute to pass some data in the event when it’s fired.

<!-- otherprops: set_clipboard -->

```nolang
<!--c:aeEvent-->
<aura:event type="APPLICATION">
    <aura:attribute name="message" type="String"/>
</aura:event>
```

## Notifier Component

The `aeNotifier.cmp` notifier component uses `aura:registerEvent` to declare that it may fire the application event. The `name` attribute is required but not used for application events. The `name` attribute is only relevant for component events.

The button in the component contains a `onclick` browser event that is wired to the `fireApplicationEvent` action in the client-side controller. Clicking this button invokes the action.

<!-- otherprops: set_clipboard -->

```nolang
<!--c:aeNotifier-->
<aura:component>
    <aura:registerEvent name="appEvent" type="c:aeEvent"/>

    <h1>Simple Application Event Sample</h1>
    <p><lightning:button
        label="Click here to fire an application event"
        onclick="{!c.fireApplicationEvent}" />
    </p>
</aura:component>
```

The client-side controller gets an instance of the event by calling `$A.get("e.c:aeEvent")`. The controller sets the `message` attribute of the event and fires the event.

<!-- otherprops: set_clipboard -->

```javascript
/* aeNotifierController.js */
{
    fireApplicationEvent : function(cmp, event) {
        // Get the application event by using the
        // e.<namespace>.<event> syntax
        var appEvent = $A.get("e.c:aeEvent");
        appEvent.setParams({
            "message" : "An application event fired me. " +
            "It all happened so fast. Now, I'm everywhere!" });
        appEvent.fire();
    }
}
```

## Handler Component

The `aeHandler.cmp` handler component uses the `<aura:handler>` tag to register that it handles the application event.

**note:** The handler for an application event won’t work if you set the `name` attribute in `<aura:handler>`. Use the `name` attribute only when you’re handling component events.

When the event is fired, the `handleApplicationEvent` action in the client-side controller of the handler component is invoked.

<!-- otherprops: set_clipboard -->

```nolang
<!--c:aeHandler-->
<aura:component>
    <aura:attribute name="messageFromEvent" type="String"/>
    <aura:attribute name="numEvents" type="Integer" default="0"/>

    <aura:handler event="c:aeEvent" action="{!c.handleApplicationEvent}"/>

    <p>{!v.messageFromEvent}</p>
    <p>Number of events: {!v.numEvents}</p>
</aura:component>
```

The controller retrieves the data sent in the event and uses it to update the `messageFromEvent` attribute in the handler component.

<!-- otherprops: set_clipboard -->

```javascript
/* aeHandlerController.js */
{
    handleApplicationEvent : function(cmp, event) {
        var message = event.getParam("message");

        // set the handler attributes based on event data
        cmp.set("v.messageFromEvent", message);
        var numEventsHandled = parseInt(cmp.get("v.numEvents")) + 1;
        cmp.set("v.numEvents", numEventsHandled);
    }
}
```

## Container Component

The `aeContainer.cmp` container component contains the notifier and handler components. This is different from the component event example where the handler contains the notifier component.

<!-- otherprops: set_clipboard -->

```nolang
<!--c:aeContainer-->
<aura:component>
    <c:aeNotifier/>
    <c:aeHandler/>
</aura:component>
```

## Put It All Together

You can test this code by adding `<c:aeContainer>` to a sample `aeWrapper.app` application and navigating to the application.

https://MY_DOMAIN_NAME.lightning.force.com/c/aeWrapper.app.

If you want to access data on the server, you could extend this example to call a server-side controller from the handler’s client-side controller.

**See Also**

- [Application Events](https://developer.salesforce.com/docs/platform/aura-platform/guide/events-application.md)
- [Creating Server-Side Logic with Controllers](https://developer.salesforce.com/docs/platform/aura-platform/controllers-server/controllers-server-intro.md)
- [Component Event Example](https://developer.salesforce.com/docs/platform/aura-platform/guide/events-component-example.md)