Use the async component to load or reload content asynchronously depending on events or page initialization. An async component can be used to either defer some content on page loads or to rerender a component. For example deferring complex components to increase the initial page load time and render this components asynchronously afterwards. Or rerendering a table after a "reload" button click or rerendering a chat view through action cable events.

The async component can be used to load or reload content asynchronously depending on page initialization or events. Simply wrap your content which you want to render asynchronously inside the async component. In order to load the content asynchronously after the initial page load use defer: true or pass in a number to delay the defer. To reload content you can use :rerender_on with an event name, leveraging the event hub, to reload the content if the specified event occurs. For example rerendering a list of todos beneath the form to create todos to instantly show new created objects. Remember events can also be used with action cable, which you could use for "real time" synchronization.


The async component is very straightforward in its usage. Every async component needs an :id, which is necessary for resolving the async component and rendering the content in the correct place afterwards. So make sure your ids for async components on the same page are unique. Specifying one of :defer or :rerender_on or both enables deferred loading and/or rerendering on events. If :defer is not configured or false the async component will be rendered on page load.

Deferring content

You can either configure an async component to request its content directly after the page load or to delay the request for a given amount of time after the page load. :defer expects either a boolean or a integer representing the delay time in milliseconds. If :defer is set to false the async component will be rendered on page load and not deferred. If set to true it will request its content directly after the page load.

def response
async id: 'deferred-async', defer: true do
plain 'Some content rendered after page is loaded.'

The above async component will be rendered asynchronously after page load.

def response
async id: 'delayed-deferred-async', defer: 500 do
plain 'Some delayed deferred content'

Specifying defer: 500 will delay the asynchronous request after page load of the async component for 300ms and render the content afterwards.

Rerendering content

The async leverages the event hub and can react to emitted events. If it receives one or more of the with :rerender_on specified events it will asynchronously request a rerender of its content. The response will only include the rerendered html of the async component which then replaces the current content of the async. If you specify multiple events in :rerender_on they need to be seperated by a comma.

def response
async id: 'rerendering-async', rerender_on: 'update-time' do
paragraph text:
onclick emit: 'update-time' do
button text: 'Update time'

The above snippet renders a paragraph with the current time and a button "Update time" on page load. If the button is clicked a update-time event is emitted. The async component wrapping the paragraph receives the event and reacts to it by requesting its rerendered content from the server and replacing its content with the received html. In this case it will rerender after button click and show the updated time.

Loading animations

An async components wraps its content in a special html structure allowing you to create animations while the components gets loaded or rerendered. It appends a loading class to the wrapping elements while the component is loading or rerendering. To learn more about how to animate loading async components checkout its api documentation.

Complete documentation

If you want to know all details about the async component checkout its api documentation‚Äč