Gadget provides the @gadgetinc/react library of React hooks for reading and writing data from your Gadget models. The useFindOne, useFindMany, useFindBy, and useGet hooks read data from your backend models and render UI with React.
Each of these hooks returns an object with the requested data, the fetching state, and an error if one was encountered, as well as a refetch function for refreshing the data if need be.
For example, if you have a model named post, we can fetch post records in a variety of ways:
React
// fetch one post by id
const [{ data, fetching, error }, refetch] = useFindOne(api.post, "10");
// fetch the first 10 posts
const [{ data, fetching, error }, refetch] = useFindMany(api.post, { first: 10 });
// fetch the first post with the slug field equal to "example-slug", throw if it isn't found
const [{ data, fetching, error }, refetch] = useFindFirst(api.post, { where: { slug: "example-slug" } });
// fetch the first post with the slug field equal to "example-slug", return null if it isn't found
const [{ data, fetching, error }, refetch] = useMaybeFindFirst(api.post, { where: { slug: "example-slug" } });
// fetch a realtime-updated view of the first 10 posts from the backend
const [{ data, fetching, error }, refetch] = useFindMany(api.post, { live: true, first: 10 });
// fetch the user's current session
const [{ data, fetching, error }, refetch] = useGet(api.currentSession);
// fetch one post by id
const [{ data, fetching, error }, refetch] = useFindOne(api.post, "10");
// fetch the first 10 posts
const [{ data, fetching, error }, refetch] = useFindMany(api.post, { first: 10 });
// fetch the first post with the slug field equal to "example-slug", throw if it isn't found
const [{ data, fetching, error }, refetch] = useFindFirst(api.post, { where: { slug: "example-slug" } });
// fetch the first post with the slug field equal to "example-slug", return null if it isn't found
const [{ data, fetching, error }, refetch] = useMaybeFindFirst(api.post, { where: { slug: "example-slug" } });
// fetch a realtime-updated view of the first 10 posts from the backend
const [{ data, fetching, error }, refetch] = useFindMany(api.post, { live: true, first: 10 });
// fetch the user's current session
const [{ data, fetching, error }, refetch] = useGet(api.currentSession);
Each of these hooks must be wrapped in a React component to render. For example, we can use useFindMany to display a list of posts in a component:
Sort on a publishedAt Date/Time field for a Post model
For more documentation on the @gadgetinc/react hooks library, see the React reference.
Writing data to models
The @gadgetinc/react React hooks library includes the useActionForm hook and the useAction hook for writing data to models by running Actions. useActionForm is suitable for building forms that give users inputs to control the input data, and useAction is a lower level hook for calling actions directly.
Building forms
With the useActionForm hook, you can manage form state and call actions easily. For example, we can build a form for a post model with useActionForm:
See the Forms guide for comprehensive docs on building forms with useActionForm.
Calling Actions directly
If you aren't building a form, or if you need lower-level control, the useAction hook can be used to call actions directly. useAction returns two values: a result object with the data from running, the fetching state, and the error if one was encountered, as well as an act function to run the backend action.
For example, with a post model on the backend, we can create a new post record by calling the act function returned by the useAction hook:
React
import { useAction } from "@gadgetinc/react";
import { api } from "../api";
const [{ data, fetching, error }, act] = useAction(api.post.create);
// when ready, run the `act` function to trigger the action
act({ title: "Example Post", body: "some post content" });
import { useAction } from "@gadgetinc/react";
import { api } from "../api";
const [{ data, fetching, error }, act] = useAction(api.post.create);
// when ready, run the `act` function to trigger the action
act({ title: "Example Post", body: "some post content" });
The same approach is used for updating data with useAction(api.post.update), but you must pass the id of the record you want to update:
React
import { useAction } from "@gadgetinc/react";
import { api } from "../api";
const [{ data, fetching, error }, act] = useAction(api.post.update);
// when ready, run the `act` function to trigger the action
act({ id: "123", title: "Example Post", body: "some new post content" });
import { useAction } from "@gadgetinc/react";
import { api } from "../api";
const [{ data, fetching, error }, act] = useAction(api.post.update);
// when ready, run the `act` function to trigger the action
act({ id: "123", title: "Example Post", body: "some new post content" });
useGlobalAction returns two values: a result object with the data from running, the fetching state, and the error if one was encountered, as well as an act function to run the backend global action.
For example, if you have a Global Action named syncData, we can run this action by calling the act function returned by the useGlobalAction hook:
React
import { useGlobalAction } from "@gadgetinc/react";
import { api } from "../api";
const [{ data, fetching, error }, act] = useGlobalAction(api.syncData);
// when ready, run the `act` function to trigger the action
act({
// any params the global action might expect
});
import { useGlobalAction } from "@gadgetinc/react";
import { api } from "../api";
const [{ data, fetching, error }, act] = useGlobalAction(api.syncData);
// when ready, run the `act` function to trigger the action
act({
// any params the global action might expect
});
We can use the useGlobalAction hook in a React component that calls the action when a button is clicked:
Backend HTTP Routes are available for calling from your frontend codebase. Calling these routes can be done with any HTTP client, but within the frontend, Gadget recommends using the useFetch hook. useFetch provides a React wrapper around the built-in browser fetch function, and includes automatic authentication support.
In a frontend React component, useFetch will make a request to a backend HTTP route. For example, if we have a api/routes/GET-hello.js file that sends a JSON reply in our backend like this:
We can call this route in a frontend React component:
React
import { useFetch } from "@gadgetinc/react";
const Component = () => {
const [{ data, fetching, error }, send] = useFetch("/hello", { json: true });
// will start out null, then when the data arrives, { message: "Hello from the backend!" }
console.log(data);
};
import { useFetch } from "@gadgetinc/react";
const Component = () => {
const [{ data, fetching, error }, send] = useFetch("/hello", { json: true });
// will start out null, then when the data arrives, { message: "Hello from the backend!" }
console.log(data);
};
Calling fetches imperatively
If you aren't using React, or would like to await a request like you might with the built-in browser fetch function, you can use the api.fetch function:
For example, we can call the /hello route from above like this:
JavaScript
const result = await api.fetch("/hello").json();
console.log(result);
// { message: "Hello from the backend!" }
const result = await api.fetch("/hello").json();
console.log(result);
// { message: "Hello from the backend!" }
api.fetch is appropriate for use in an imperative context, like a server-side script, or other places where you don't need to give the user feedback about what's happening. useFetch is appropriate when you need to show the user feedback as the fetching or error state changes.
Maintaining session state when calling HTTP routes
Different apps use different mechanisms to authenticate requests from the client to your Gadget backend. When making raw HTTP calls to your backend, you need to ensure that the correct authentication headers are passed to your backend. The api client object provided by Gadget sends these headers automatically for GraphQL requests and requests made by the React hooks.
The useFetch hook and api.fetch function implements this same automatic authentication header setting but for any HTTP request to the backend. useFetch and api.fetch wrap the browser built-in fetch, but add the headers required to implement whichever authentication mode is active for your app.
The different authentication modes are documented in your API reference.
Here's an example user component that uses useFetch to make a request to a api/routes/users/GET-me.js backend Gadget route:
React
export function UserByEmail() {
const [{ data, fetching, error }, refresh] = useFetch("/users/me", {
method: "GET",
json: true,
});
if (error) return <>Error: {error.toString()}</>;
if (fetching) return <>Fetching...</>;
if (!data) return <>No user found</>;
return <div>{data.name}</div>;
}
export function UserByEmail() {
const [{ data, fetching, error }, refresh] = useFetch("/users/me", {
method: "GET",
json: true,
});
if (error) return <>Error: {error.toString()}</>;
if (fetching) return <>Fetching...</>;
if (!data) return <>No user found</>;
return <div>{data.name}</div>;
}
Request method
By default, GET requests are sent as soon as the hook executes. GET requests can also be refreshed by calling the second return value to re-send the fetch request and fetch fresh data.
React
// GET request will be sent immediately, can be refreshed by calling `refresh()` again
const [{ data, fetching, error }, refresh] = useFetch("/some/route", { method: "GET" });
// ... sometime later
// `data` will now be populated
data;
// GET request will be sent immediately, can be refreshed by calling `refresh()` again
const [{ data, fetching, error }, refresh] = useFetch("/some/route", { method: "GET" });
// ... sometime later
// `data` will now be populated
data;
Other request methods like POST, DELETE, etc will not be sent automatically. The request will only be sent when the send functions is called explicitly, often in a click handler or similar.
React
// POST requests are not sent immediately. They will only be sent when `send()` is called
const [{ data, fetching, error }, send] = useFetch("/some/route", { method: "POST" });
useEffect(() => {
async function callRoute() {
// make request to '/some/route' http route
await send();
}
void callRoute();
}, []);
// will be undefined until the useEffect is run
// and send() is called and request is completed
console.log(data);
// POST requests are not sent immediately. They will only be sent when `send()` is called
const [{ data, fetching, error }, send] = useFetch("/some/route", { method: "POST" });
useEffect(() => {
async function callRoute() {
// make request to '/some/route' http route
await send();
}
void callRoute();
}, []);
// will be undefined until the useEffect is run
// and send() is called and request is completed
console.log(data);
Retrieving JSON
useFetch has a handy json: true option for automatically parsing a JSON response from the server. If you know your route will return JSON, you can set this option to true and the response will be parsed and returned as an object.
React
import { useFetch } from "@gadgetinc/react";
export function User() {
const [{ data, fetching, error }, refresh] = useFetch("/users/me", {
method: "GET",
json: true,
});
if (error) return <>Error: {error.toString()}</>;
if (fetching) return <>Fetching...</>;
if (!data) return <>No user found</>;
// no need to JSON.parse the result
return <div>{data.name}</div>;
}
import { useFetch } from "@gadgetinc/react";
export function User() {
const [{ data, fetching, error }, refresh] = useFetch("/users/me", {
method: "GET",
json: true,
});
if (error) return <>Error: {error.toString()}</>;
if (fetching) return <>Fetching...</>;
if (!data) return <>No user found</>;
// no need to JSON.parse the result
return <div>{data.name}</div>;
}
The json: true option does not affect what is sent with your request, and only affects how the response is processed.
Sending JSON
To send a JSON formatted request with the useFetch hook, JSON.stringify your request body and set the content-type: application/json header:
The @gadgetinc/react hooks library includes a useFetch hook, but if you'd like to use your preferred HTTP hook library, you can! By wrapping api.fetch with one of the great existing React libraries for making HTTP calls, like use-http, swr or react-query, you can continue passing the same authentication state and headers to your backend.
For example, we call a /example route in the backend with the swr library. First, create the route by adding the api/routes/GET-example.js file:
api/routes/GET-example.js
JavaScript
import { RouteHandler } from "gadget-server";
const route: RouteHandler = async ({ reply }) => {
reply.send({ message: "Hello from the backend!" });
};
export default route;
import { RouteHandler } from "gadget-server";
const route: RouteHandler = async ({ reply }) => {
reply.send({ message: "Hello from the backend!" });
};
export default route;
Next, install swr into your application by adding the following to package.json and clicking the Run Yarn button:
package.json
json
{
"swr": "^2.0.4"
}
Then, in your React component, import the useSWR hook from swr and the api.fetch function from your Gadget API client:
React
import useSWR from "swr";
import { api } from "../api";
const fetcher = (args: RequestInfo | URL) => api.fetch(args).then((res) => res.json());
function Profile() {
const { data, error } = useSWR("/example", fetcher);
if (error) return <div>failed to load</div>;
if (!data) return <div>loading...</div>;
return <div>Backend message: {data.message}!</div>;
}
import useSWR from "swr";
import { api } from "../api";
const fetcher = (args: RequestInfo | URL) => api.fetch(args).then((res) => res.json());
function Profile() {
const { data, error } = useSWR("/example", fetcher);
if (error) return <div>failed to load</div>;
if (!data) return <div>loading...</div>;
return <div>Backend message: {data.message}!</div>;
}
Static asset handling
Gadget's frontend hosting supports serving static assets in a robust, CDN-friendly way using Vite. You can add static assets anywhere within your web directory, and then import them into your code. For example, if you add an image at web/images/hero.png, you can import it in your frontend code like this:
When you `import` a static asset in your frontend code, Vite will produce an appropriate URL for that asset that works well in both development and production.
Production asset links
When you deploy to production, Gadget runs your app's build process, and Vite builds production-safe URLs for all your static assets. These URLs include a cache hash, which means that each new version of your asset gets a unique URL. These unique URLs allow Gadget's CDN to cache the asset for maximum performance, and ensures users get new versions as soon as you deploy by changing the url.
If you change these static assets, Vite will generate a new hash and the updated asset will be loaded from Gadget's CDN on the next page render.
Non-transformed public assets
Gadget's frontend can host assets that aren't transformed by Vite, like your app's favicon or a robots.txt file. Instead of being minified and cached by vite, these files will be served as-is from your app's filesystem.
You can store these assets in a public folder at the root level of your Gadget project.
Where possible, prefer using import-ed assets in your code instead of storing them in the public folder. This way, Vite can
automatically manage CDN cache expiry for you.
For example, if you have a public folder in your application like this:
public/
favicon.ico
robots.txt
foo/
bar.txt
You can access your robots.txt file by making a request to:
https://example-app--development.gadget.app/robots.txt in development
https://example-app.gadget.app/robots.txt in production once deployed
The public folder also supports sub-folders. You can access the public/foo/bar.txt file by making a request to:
https://example-app--development.gadget.app/foo/bar.txt in development
https://example-app.gadget.app/foo/bar.txt in production once deployed
Production cache expiry for non-transformed public assets
Gadget automatically caches all assets, both transformed assets from within web and non-transformed assets from public within public, on a high-performance CDN. Gadget also sets browser caching headers for these assets so browsers won't re-download them every page load, which improves user experience.
To maximize the cache hit rate for the best user experience, assets are cached by URL for long durations. For assets in the public folder, this means that when you change an asset, the new version will not be served to users until the cache expires.
If you change an asset, you can force a cache bust by changing the URL. For example, if you have a robots.txt file in your public folder, you can force a cache bust by changing the URL to https://example-app--development.gadget.app/robots.txt?v=2.
If you want to force a cache bust for all assets, you can add a query parameter to the URL. For example, you can add a query parameter to the URL to force a cache bust for all assets: https://example-app--development.gadget.app/robots.txt?v=2.
This cache busting process is automatically managed by Vite for assets you import in the web folder, so Gadget recommends using import-ed assets in your code instead of storing them in the public folder where possible.
Vite configuration
Gadget exposes the vite.config.mjs file that powers the Vite integration hosting your frontend. In vite.config.mjs, you can adjust the set of Vite plugins that power your application.
For example, we can add [MDX] support to a Gadget frontend with the @mdx-js/rollup plugin. First, install the plugin by adding the following to package.json and clicking the Run Yarn button:
package.json
json
{
"@mdx-js/rollup": "^2.3.0"
}
Then, in our vite.config.mjs, we can add the plugin to the list of plugins:
vite.config.mjs
JavaScript
import react from "@vitejs/plugin-react";
import mdx from "@mdx-js/rollup";
import { defineConfig } from "vite";
export default defineConfig({
plugins: [
// newly added mdx plugin, configured as MDX recommends in their docs: https://mdxjs.com/docs/getting-started/#vite
{ enforce: "pre", ...mdx() },
// leave the existing react plugin in place
react(),
],
base: "/",
});
import react from "@vitejs/plugin-react";
import mdx from "@mdx-js/rollup";
import { defineConfig } from "vite";
export default defineConfig({
plugins: [
// newly added mdx plugin, configured as MDX recommends in their docs: https://mdxjs.com/docs/getting-started/#vite
{ enforce: "pre", ...mdx() },
// leave the existing react plugin in place
react(),
],
base: "/",
});