useResource$() - Explicit Reactivity

For this tutorial, we would like to fetch the list of repositories for a given GitHub organization. To aid you, we have added the getRepositories() function to the bottom of the file. Your task is to use the getRepositories() function to fetch the list of repositories whenever the user updates the org input.

Qwik provides useResource$() and <Resource> to help you fetch and display data from the server. When fetching data the application can be in one of three states:

• pending: the data is being fetched from the server => Render loading... indicator.
• resolved: the data has successfully been fetched from the server => Render the data.
• rejected: the data could not be fetched from the server due to an error => Render the error.

Use useResource$() function to set up how the data is fetched from the server. Use <Resource> to display the data.

Fetching data

Use useResource$() to set up how the data is fetched from the server.

  const reposResource = useResource$<string[]>(({ track, cleanup }) => {
    // We need a way to re-run fetching data whenever the `github.org` changes.
    // Use `track` to trigger re-running of this data fetching function.
    track(() => github.org);
 
    // A good practice is to use `AbortController` to abort the fetching of data if
    // new request comes in. We create a new `AbortController` and register a `cleanup`
    // function which is called when this function re-runs.
    const controller = new AbortController();
    cleanup(() => controller.abort());
 
    // Fetch the data and return the promises.
    return getRepositories(github.org, controller);
  });

The useResource$() function returns a ResourceReturn object, which is a Promise-like object that can be serialized by Qwik. The useResource$() function allows you to track store properties so that the useResource$() function can be reactive on store changes. The cleanup function allows you to register a code that needs to be run to release resources from the previous run. Finally, the useResource$() function returns a promise that will resolve to the value.

Rendering data

Use <Resource> to display the data of the useResource$() function. The <Resource> allows you to render different content depending if the resource is pending, resolved or rejected.

On the server the <Resource> does not render loading state, instead, it pauses rendering until the resource is resolved and will always render as either resolved or rejected. (On the client, the <Resource> renders all states including pending.)

<Resource
  value={resourceToRender}
  onPending={() => <div>Loading...</div>}
  onRejected={(reason) => <div>Error: {reason}</div>}
  onResolved={(data) => <div>{data}</div>}
/>

SSR vs Client

Notice that the same code can render on both server and client (with slightly different behavior, which skips the pending state rendering on the server.)

Next: Using context