Loader und Actions (Data Router API)

Was sind Loader?

Einen Loader definieren

import { createBrowserRouter } from 'react-router-dom';

async function userLoader({ params }) {
  const res = await fetch(`/api/users/${params.id}`);
  if (!res.ok) throw new Response('Not Found', { status: 404 });
  return res.json();
}

const router = createBrowserRouter([
  { path: '/users/:id', element: <UserDetail />, loader: userLoader },
]);

Loader-Daten mit useLoaderData auslesen

import { useLoaderData } from 'react-router-dom';

function UserDetail() {
  const user = useLoaderData();
  return <h1>{user.name}</h1>;
}

Was sind Actions?

async function createUserAction({ request }) {
  const formData = await request.formData();
  const name = formData.get('name');
  await fetch('/api/users', {
    method: 'POST',
    body: JSON.stringify({ name }),
    headers: { 'Content-Type': 'application/json' },
  });
  return redirect('/users');
}

Actions mit Form auslösen

import { Form } from 'react-router-dom';

function NewUser() {
  return (
    <Form method="post">
      <input name="name" />
      <button type="submit">Create</button>
    </Form>
  );
}

Daten aus Actions zurückgeben

async function loginAction({ request }) {
  const data = await request.formData();
  const errors = validate(data);
  if (errors) return errors; // returned to useActionData
  await login(data);
  return redirect('/dashboard');
}

function Login() {
  const errors = useActionData();
  return (
    <Form method="post">
      {errors?.email && <p>{errors.email}</p>}
      <input name="email" />
    </Form>
  );
}

Ladezustände mit useNavigation

function SubmitButton() {
  const navigation = useNavigation();
  const isSubmitting = navigation.state === 'submitting';
  return (
    <button type="submit" disabled={isSubmitting}>
      {isSubmitting ? 'Saving...' : 'Save'}
    </button>
  );
}

Verzögerte Daten mit defer()

import { defer, Await } from 'react-router-dom';

async function slowLoader() {
  return defer({ fast: await getFast(), slow: getSlow() });
}

function Page() {
  const { fast, slow } = useLoaderData();
  return (
    <>
      <h1>{fast.title}</h1>
      <Suspense fallback={<p>Loading...</p>}>
        <Await resolve={slow}>{data => <Chart data={data} />}</Await>
      </Suspense>
    </>
  );
}

Revalidierung nach Actions

Fehlerbehandlung in Loadern

function ErrorPage() {
  const error = useRouteError();
  return (
    <div>
      <h1>{error.status} {error.statusText}</h1>
    </div>
  );
}

Fetchers für Mutationen ohne Navigation

function LikeButton({ postId }) {
  const fetcher = useFetcher();
  return (
    <fetcher.Form method="post" action={`/posts/${postId}/like`}>
      <button type="submit">Like</button>
    </fetcher.Form>
  );
}

Schnelltest

Zusammenfassung