Optimistic Updates

Optimistic updates enable highly responsive and fast interfaces by avoiding network wait times. An update is optimistic by assuming the network is successful. In the case of any errors, Rest Hooks will then roll back any changes in a way that deals with all possible race conditions.

Partial updates

One common use case is for quick toggles. Here we demonstrate a publish button for an article. Note that we need to include the primary key (id in this case) in the response body to ensure the normalized cache gets updated correctly.

ArticleResource.ts

import {
  MutateEndpoint,
  SchemaDetail,
  AbstractInstanceType,
} from 'rest-hooks';
import { Resource } from '@rest-hooks/rest';

export default class ArticleResource extends Resource {
  readonly id: string | undefined = undefined;
  readonly title: string = '';
  readonly content: string = '';
  readonly published: boolean = false;

  pk() {
    return this.id;
  }

  static partialUpdate<T extends typeof Resource>(
    this: T,
  ): MutateEndpoint<
    (p: Readonly<object>, b: Partial<AbstractInstanceType<T>>) => Promise<any>,
    SchemaDetail<Readonly<AbstractInstanceType<T>>>
  > {
    return super.partialUpdate().extend({
      optimisticUpdate: (params: any, body: any) => ({
        // we absolutely need the primary key here,
        // but won't be sent in a partial update
        id: params.id,
        ...body,
      }),
    });
  }
}

PublishButton.tsx

import { useFetcher } from 'rest-hooks';
import ArticleResource from 'ArticleResource';

export default function PublishButton({ id }: { id: string }) {
  const update = useFetcher(ArticleResource.partialUpdate());

  return (
    <button onClick={() => update({ id }, { published: true })}>Publish</button>
  );
}

Optimistic create with instant updates

Optimistic updates can also be combined with immediate updates, enabling updates to other endpoints instantly. This is most commonly seen when creating new items while viewing a list of them.

Here we demonstrate what could be used in a list of articles with a modal to create a new article. On submission of the form it would instantly add to the list of articles the newly created article - without waiting on a network response.

ArticleResource.ts

import {
  MutateEndpoint,
  AbstractInstanceType,
} from 'rest-hooks';
import { SchemaDetail, Resource } from '@rest-hooks/rest';

export default class ArticleResource extends Resource {
  readonly id: string | undefined = undefined;
  readonly title: string = '';
  readonly content: string = '';
  readonly published: boolean = false;

  pk() {
    return this.id;
  }

  static create<T extends typeof Resource>(
    this: T,
  ): MutateEndpoint<
    (p: Readonly<object>, b: Partial<AbstractInstanceType<T>>) => Promise<any>,
    SchemaDetail<Readonly<AbstractInstanceType<T>>>
  > {
    return super.create().extend({
      optimisticUpdate: (
        params: Readonly<object>,
        body: Readonly<object | string> | void,
      ) => body,
    });
  }
}

export const appendUpdater = (
  newArticleID: string,
  articleIDs: string[] | undefined,
) => [...(articleIDs || []), newArticleID];

CreateArticle.tsx

Since the actual id of the article is created on the server, we will need to fill in a temporary fake id here, so the primary key can be generated. This is needed to properly normalize the article to be looked up in the cache.

Once the network responds, it will have a different id, which will replace the existing data. This is often seamless, but care should be taken if the fake id is used in any renders - like to issue subsequent requests. We recommend disabling edit type features that rely on the primary key until the network fetch completes.

import { useFetcher } from 'rest-hooks';
import uuid from 'uuid/v4';
import ArticleResource from 'ArticleResource';

export default function CreateArticle() {
  const create = useFetcher(ArticleResource.create());
  const submitHandler = useCallback(
    data =>
      // note the fake id we create.
      create({}, { id: uuid(), ...data }, [
        [ArticleResource.list(), {}, appendUpdater],
      ]),
    [create],
  );

  return <Form onSubmit={submitHandler}>{/* rest of form */}</Form>;
}

Optimistic Deletes

Since deletes automatically update the cache correctly upon fetch success, making your delete endpoint do this optimistically is as easy as adding the optimisticUpdate function to your options.

We return an empty string because that's the response we expect from the server. Although by default, the server response is ignored.

import { Resource, SimpleResource } from '@rest-hooks/rest';
import { MutateEndpoint } from 'rest-hooks';

export default class ArticleResource extends Resource {
  readonly id: string | undefined = undefined;
  readonly title: string = '';
  readonly content: string = '';
  readonly published: boolean = false;

  pk() {
    return this.id;
  }

  static delete<T extends typeof Resource>(
    this: T,
  ): MutateEndpoint<(p: Readonly<object>) => Promise<any>, schemas.Delete<T>> {
    return super.delete().extend({
      optimisticUpdate: (params: any, body: any) => params,
    });
  }
}