useFetch

Hook which fetches the URL and returns the AsyncState corresponding to the execution of the fetch.

It follows the stale-while-revalidate cache invalidation strategy popularized by HTTP RFC 5861. useFetch first returns the data from cache (stale), then sends the request (revalidate), and finally comes with the up-to-date data again.

The last value will be kept between command runs.

Signature

export function useFetch<V, U, T = V>(
  url: RequestInfo,
  options?: RequestInit & {
    parseResponse?: (response: Response) => Promise<V>;
    mapResult?: (result: V) => { data: T };
    initialData?: U;
    keepPreviousData?: boolean;
    execute?: boolean;
    onError?: (error: Error) => void;
    onData?: (data: T) => void;
    onWillExecute?: (args: [string, RequestInit]) => void;
  },
): AsyncState<T> & {
  revalidate: () => void;
  mutate: MutatePromise<T | U | undefined>;
};

Arguments

• url is the string representation of the URL to fetch.

With a few options:

• options extends RequestInit allowing you to specify a body, headers, etc. to apply to the request.

• options.parseResponse is a function that accepts the Response as an argument and returns the data the hook will return. By default, the hook will return response.json() if the response has a JSON Content-Type header or response.text() otherwise.

• options.mapResult is an optional function that accepts whatever options.parseResponse returns as an argument, processes the response, and returns an object wrapping the result, i.e. (response) => { return { data: response> } };.

Including the useCachedPromise's options:

• options.keepPreviousData is a boolean to tell the hook to keep the previous results instead of returning the initial value if there aren't any in the cache for the new arguments. This is particularly useful when used for data for a List to avoid flickering. See Argument dependent on List search text for more information.

Including the useCachedState's options:

• options.initialData is the initial value of the state if there aren't any in the Cache yet.

Including the usePromise's options:

• options.execute is a boolean to indicate whether to actually execute the function or not. This is useful for cases where one of the function's arguments depends on something that might not be available right away (for example, depends on some user inputs). Because React requires every hook to be defined on the render, this flag enables you to define the hook right away but wait until you have all the arguments ready to execute the function.

• options.onError is a function called when an execution fails. By default, it will log the error and show a generic failure toast with an action to retry.

• options.onData is a function called when an execution succeeds.

• options.onWillExecute is a function called when an execution will start.

Return

Returns an object with the AsyncState corresponding to the execution of the fetch as well as a couple of methods to manipulate it.

• data, error, isLoading - see AsyncState.

• revalidate is a method to manually call the function with the same arguments again.

• mutate is a method to wrap an asynchronous update and gives some control over how the useFetch's data should be updated while the update is going through. By default, the data will be revalidated (eg. the function will be called again) after the update is done. See Mutation and Optimistic Updates for more information.

Example

import { Detail, ActionPanel, Action } from "@raycast/api";
import { useFetch } from "@raycast/utils";

export default function Command() {
  const { isLoading, data, revalidate } = useFetch("https://api.example");

  return (
    <Detail
      isLoading={isLoading}
      markdown={data}
      actions={
        <ActionPanel>
          <Action title="Reload" onAction={() => revalidate()} />
        </ActionPanel>
      }
    />
  );
}

Argument dependent on List search text

By default, when an argument passed to the hook changes, the function will be executed again and the cache's value for those arguments will be returned immediately. This means that in the case of new arguments that haven't been used yet, the initial data will be returned.

This behaviour can cause some flickering (initial data -> fetched data -> arguments change -> initial data -> fetched data, etc.). To avoid that, we can set keepPreviousData to true and the hook will keep the latest fetched data if the cache is empty for the new arguments (initial data -> fetched data -> arguments change -> fetched data).

import { useState } from "react";
import { List, ActionPanel, Action } from "@raycast/api";
import { useFetch } from "@raycast/utils";

export default function Command() {
  const [searchText, setSearchText] = useState("");
  const { isLoading, data } = useFetch(`https://api.example?q=${searchText}`, {
    // to make sure the screen isn't flickering when the searchText changes
    keepPreviousData: true,
  });

  return (
    <List isLoading={isLoading} searchText={searchText} onSearchTextChange={setSearchText} throttle>
      {(data || []).map((item) => (
        <List.Item key={item.id} title={item.title} />
      ))}
    </List>
  );
}

Mutation and Optimistic Updates

In an optimistic update, the UI behaves as though a change was successfully completed before receiving confirmation from the server that it was - it is being optimistic that it will eventually get the confirmation rather than an error. This allows for a more responsive user experience.

You can specify an optimisticUpdate function to mutate the data in order to reflect the change introduced by the asynchronous update.

When doing so, you can specify a rollbackOnError function to mutate back the data if the asynchronous update fails. If not specified, the data will be automatically rolled back to its previous value (before the optimistic update).

import { Detail, ActionPanel, Action, showToast, Toast } from "@raycast/api";
import { useFetch } from "@raycast/utils";

export default function Command() {
  const { isLoading, data, mutate } = useFetch("https://api.example");

  const appendFoo = async () => {
    const toast = await showToast({ style: Toast.Style.Animated, title: "Appending Foo" });
    try {
      await mutate(
        // we are calling an API to do something
        fetch("https://api.example/append-foo"),
        {
          // but we are going to do it on our local data right away,
          // without waiting for the call to return
          optimisticUpdate(data) {
            return data + "foo";
          },
        },
      );
      // yay, the API call worked!
      toast.style = Toast.Style.Success;
      toast.title = "Foo appended";
    } catch (err) {
      // oh, the API call didn't work :(
      // the data will automatically be rolled back to its previous value
      toast.style = Toast.Style.Failure;
      toast.title = "Could not append Foo";
      toast.message = err.message;
    }
  };

  return (
    <Detail
      isLoading={isLoading}
      markdown={data}
      actions={
        <ActionPanel>
          <Action title="Append Foo" onAction={() => appendFoo()} />
        </ActionPanel>
      }
    />
  );
}

Pagination

When paginating, the hook will only cache the result of the first page.

The hook has built-in support for pagination. In order to enable pagination, urls type needs to change from RequestInfo to a function that receives a PaginationOptions argument, and returns a RequestInfo.

In practice, this means going from

const { isLoading, data } = useFetch(
  "https://api.ycombinator.com/v0.1/companies?" + new URLSearchParams({ q: searchText }).toString(),
  {
    mapResult(result: SearchResult) {
      return {
        data: result.companies,
      };
    },
    keepPreviousData: true,
    initialData: [],
  },
);

to

const { isLoading, data, pagination } = useFetch(
  (options) =>
    "https://api.ycombinator.com/v0.1/companies?" +
    new URLSearchParams({ page: String(options.page + 1), q: searchText }).toString(),
  {
    mapResult(result: SearchResult) {
      return {
        data: result.companies,
        hasMore: result.page < result.totalPages,
      };
    },
    keepPreviousData: true,
    initialData: [],
  },
);

You'll notice that, in the second case, the hook returns an additional item: pagination. This can be passed to Raycast's List or Grid components in order to enable pagination. Another thing to notice is that mapResult, which is normally optional, is actually required when using pagination. Furthermore, its return type is

{
  data: any[],
  hasMore?: boolean;
}

Every time the URL is fetched, the hook needs to figure out if it should paginate further, or if it should stop, and it uses the hasMore for this. In addition to this, the hook also needs data, and needs it to be an array, because internally it appends it to a list, thus making sure the data that the hook returns always contains the data for all of the pages that have been fetched so far.

Full Example

import { Icon, Image, List } from "@raycast/api";
import { useFetch } from "@raycast/utils";
import { useState } from "react";

type SearchResult = { companies: Company[]; page: number; totalPages: number };
type Company = { id: number; name: string; smallLogoUrl?: string };
export default function Command() {
  const [searchText, setSearchText] = useState("");
  const { isLoading, data, pagination } = useFetch(
    (options) =>
      "https://api.ycombinator.com/v0.1/companies?" +
      new URLSearchParams({ page: String(options.page + 1), q: searchText }).toString(),
    {
      mapResult(result: SearchResult) {
        return {
          data: result.companies,
          hasMore: result.page < result.totalPages,
        };
      },
      keepPreviousData: true,
      initialData: [],
    },
  );

  return (
    <List isLoading={isLoading} pagination={pagination} onSearchTextChange={setSearchText}>
      {data.map((company) => (
        <List.Item
          key={company.id}
          icon={{ source: company.smallLogoUrl ?? Icon.MinusCircle, mask: Image.Mask.RoundedRectangle }}
          title={company.name}
        />
      ))}
    </List>
  );
}

Types

AsyncState

An object corresponding to the execution state of the function.

// Initial State
{
  isLoading: true, // or `false` if `options.execute` is `false`
  data: undefined,
  error: undefined
}

// Success State
{
  isLoading: false,
  data: T,
  error: undefined
}

// Error State
{
  isLoading: false,
  data: undefined,
  error: Error
}

// Reloading State
{
  isLoading: true,
  data: T | undefined,
  error: Error | undefined
}

MutatePromise

A method to wrap an asynchronous update and gives some control about how the useFetch's data should be updated while the update is going through.

export type MutatePromise<T> = (
  asyncUpdate?: Promise<any>,
  options?: {
    optimisticUpdate?: (data: T) => T;
    rollbackOnError?: boolean | ((data: T) => T);
    shouldRevalidateAfter?: boolean;
  },
) => Promise<any>;

PaginationOptions

An object passed to a PaginatedRequestInfo, it has two properties:

• page: 0-indexed, this it's incremented every time the promise resolves, and is reset whenever revalidate() is called.

• lastItem: this is a copy of the last item in the data array from the last time the promise was executed. Provided for APIs that implement cursor-based pagination.

• cursor: this is the cursor property returned after the previous execution of PaginatedPromise. Useful when working with APIs that provide the next cursor explicitly.

export type PaginationOptions<T = any> = {
  page: number;
  lastItem?: T;
  cursor?: any;
};