useFetch
Hook which fetches the URL and returns the AsyncState corresponding to the execution of the fetch. The last value will be kept between command runs.

Signature

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

Arguments

  • url is the string representation of the URL to fetch.
  • 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 hooks will return. But default, the hook will return response.json() if the response has a JSON Content-Type header or response.text() otherwise.
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.
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.abortable is a reference to an AbortController to cancel a previous call when triggering a new one.
  • 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 function 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 { useFetch } from "@raycast/utils";
const Demo = () => {
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";
const Demo = () => {
const [searchText, setSearchText] = useState("");
const { isLoading, data, mutate } = 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";
const Demo = () => {
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>
}
/>
);
};

Types

AsyncState

An object corresponding to the execution state of the function.
// Initial State
{
isLoading: true,
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>;