useSuspense()

High performance async data rendering without overfetching.

useSuspense() suspends rendering until the data is available. This is much like awaiting an async function. This avoids the complexity of handling loading and error conditions in your components by centralizing them with a singular AsyncBoundary.

Usage

Fixtures

GET /profiles/1

{"id":"1","fullName":"Einstein","bio":"Smart physicist"}

GET /profiles/2

{"id":"2","fullName":"Elon Musk","bio":"CEO of Tesla, SpaceX and owner of Twitter"}

▶api/Profile

import { Entity, createResource } from '@rest-hooks/rest';

export class Profile extends Entity {
  id: number | undefined = undefined;
  img = '';
  fullName = '';
  bio = '';

  pk() {
    return this.id?.toString();
  }
}

export const ProfileResource = createResource({
  path: '/profiles/:id',
  schema: Profile,
});

▶ProfileList

import { useSuspense } from '@rest-hooks/react';
import { ProfileResource } from './api/Profile';

function ProfileDetail(): JSX.Element {
  const profile = useSuspense(ProfileResource.get, { id: 1 });
  return (
    <div>
      <h4>{profile.fullName}</h4>
      <p>{profile.bio}</p>
    </div>
  );
}
render(<ProfileDetail />);

Live Preview

Loading...

Store▶

Behavior

Cache policy is Stale-While-Revalidate by default but also configurable.

Expiry Status	Fetch	Suspend	Error	Conditions
Invalid	yes1	yes	no	not in store, deletion, invalidation, invalidIfStale
Stale	yes1	no	no	(first-render, arg change) & expiry < now
Valid	no	no	maybe2	fetch completion
	no	no	no	null used as second argument

note

1. Identical fetches are automatically deduplicated
2. Hard errors to be caught by Error Boundaries

React Native

When using React Navigation, useSuspense() will trigger fetches on focus if the data is considered stale.

Conditional Dependencies

Use null as the second argument on any rest hooks to indicate "do nothing."

// todo could be undefined if id is undefined
const todo = useSuspense(TodoResource.get, id ? { id } : null);

Types

Type

function useSuspense(
  endpoint: ReadEndpoint,
  ...args: Parameters<typeof endpoint> | [null]
): Denormalize<typeof endpoint.schema>;

With Generics

function useSuspense<
  E extends EndpointInterface<FetchFunction, Schema | undefined, undefined>,
  Args extends readonly [...Parameters<E>] | readonly [null],
>(
  endpoint: E,
  ...args: Args
): E['schema'] extends Exclude<Schema, null>
  ? Denormalize<E['schema']>
  : ReturnType<E>;

Examples

List

Fixtures

GET /profiles

[{"id":"1","fullName":"Einstein","bio":"Smart physicist"},{"id":"2","fullName":"Elon Musk","bio":"CEO of Tesla, SpaceX and owner of Twitter"}]

▶api/Profile

import { Entity, createResource } from '@rest-hooks/rest';

export class Profile extends Entity {
  id: number | undefined = undefined;
  img = '';
  fullName = '';
  bio = '';

  pk() {
    return this.id?.toString();
  }
}

export const ProfileResource = createResource({
  path: '/profiles/:id',
  schema: Profile,
});

▶ProfileList

import { useSuspense } from '@rest-hooks/react';
import { ProfileResource } from './api/Profile';

function ProfileList(): JSX.Element {
  const profiles = useSuspense(ProfileResource.getList);
  return (
    <div>
      {profiles.map(profile => (
        <div key={profile.pk()}>
          <h4>{profile.fullName}</h4>
          <p>{profile.bio}</p>
        </div>
      ))}
    </div>
  );
}
render(<ProfileList />);

Live Preview

Loading...

Store▶

Sequential

When fetch parameters depend on data from another resource.

function PostWithAuthor() {
  const post = useSuspense(PostResource.get, { id });
  // post as Post
  const author = useSuspense(UserResource.get, {
    id: post.userId,
  });
  // author as User
}

Embedded data

When entities are stored in nested structures, that structure will remain.

▶api/Post

export class PaginatedPost extends Entity {
  id = '';
  title = '';
  content = '';

  pk() {
    return this.id;
  }
}

export const getPosts = new RestEndpoint({
  path: '/post',
  searchParams: { page: '' },
  schema: { results: [PaginatedPost], nextPage: '', lastPage: '' },
});

▶ArticleList

import { getPosts } from './api/Post';

export default function ArticleList({ page }: { page: string }) {
  const {
    results: posts,
    nextPage,
    lastPage,
  } = useSuspense(getPosts, { page });
  return (
    <div>
      {posts.map(post => (
        <div key={post.pk()}>{post.title}</div>
      ))}
    </div>
  );
}

Todo App

Explore more Rest Hooks demos