docs: useFetcher examples (#203)

examples/react-router/src/App.tsx

@@ -11,6 +11,7 @@ const router = createBrowserRouter(
 	createRoutesFromElements(
 		<Route path="/" Component={Example}>
 			<Route path="login" lazy={() => import('./login')} />
+			<Route path="login-fetcher" lazy={() => import('./login-fetcher')} />
 			<Route path="todos" lazy={() => import('./todos')} />
 			<Route path="signup" lazy={() => import('./signup')} />
 		</Route>,
@@ -30,7 +31,8 @@ function Example() {
 
 			<ul>
 				<li>
-					<Link to="login">Login</Link>
+					<Link to="login">Login</Link> (
+					<Link to="login-fetcher">with useFetcher</Link>)
 				</li>
 				<li>
 					<Link to="todos">Todo list</Link>

examples/react-router/src/login-fetcher.tsx

@@ -0,0 +1,86 @@
+import type { Submission } from '@conform-to/react';
+import { useForm, parse, validateConstraint } from '@conform-to/react';
+import type { ActionFunctionArgs } from 'react-router-dom';
+import { useFetcher, json, redirect } from 'react-router-dom';
+
+interface Login {
+	email: string;
+	password: string;
+	remember: string;
+}
+
+async function isAuthenticated(email: string, password: string) {
+	return new Promise((resolve) => {
+		resolve(email === '[email protected]' && password === '12345');
+	});
+}
+
+export async function action({ request }: ActionFunctionArgs) {
+	const formData = await request.formData();
+	const submission = parse(formData);
+
+	if (
+		!(await isAuthenticated(
+			submission.payload.email,
+			submission.payload.password,
+		))
+	) {
+		return json({
+			...submission,
+			// '' denote the root which is treated as form error
+			error: { '': 'Invalid credential' },
+		});
+	}
+
+	return redirect('/');
+}
+
+export function Component() {
+	const fetcher = useFetcher<Submission>();
+	const [form, { email, password }] = useForm<Login>({
+		lastSubmission: fetcher.data,
+		shouldRevalidate: 'onBlur',
+		onValidate(context) {
+			return validateConstraint(context);
+		},
+	});
+
+	return (
+		<fetcher.Form method="post" {...form.props}>
+			<div className="form-error">{form.error}</div>
+			<label>
+				<div>Email</div>
+				<input
+					className={email.error ? 'error' : ''}
+					name="email"
+					type="email"
+					required
+					pattern="[^@]+@[^@]+\.[^@]+"
+				/>
+				{email.error === 'required' ? (
+					<div>Email is required</div>
+				) : email.error === 'type' || email.error === 'pattern' ? (
+					<div>Email is invalid</div>
+				) : null}
+			</label>
+			<label>
+				<div>Password</div>
+				<input
+					className={password.error ? 'error' : ''}
+					name="password"
+					type="password"
+					required
+				/>
+				{password.error === 'required' ? <div>Password is required</div> : null}
+			</label>
+			<label>
+				<div>
+					<span>Remember me</span>
+					<input name="remember" type="checkbox" value="yes" />
+				</div>
+			</label>
+			<hr />
+			<button>Login</button>
+		</fetcher.Form>
+	);
+}

examples/react-router/src/login.tsx

@@ -1,8 +1,7 @@
 import type { Submission } from '@conform-to/react';
 import { useForm, parse, validateConstraint } from '@conform-to/react';
 import type { ActionFunctionArgs } from 'react-router-dom';
-import { Form, useActionData } from 'react-router-dom';
-import { json, redirect } from 'react-router-dom';
+import { Form, useActionData, json, redirect } from 'react-router-dom';
 
 interface Login {
 	email: string;
@@ -40,7 +39,7 @@ export function Component() {
 	const lastSubmission = useActionData() as Submission;
 	const [form, { email, password }] = useForm<Login>({
 		lastSubmission,
-		shouldValidate: 'onBlur',
+		shouldRevalidate: 'onBlur',
 		onValidate(context) {
 			return validateConstraint(context);
 		},

examples/remix/app/root.tsx

@@ -39,7 +39,8 @@ export default function App() {
 
 					<ul>
 						<li>
-							<Link to="login">Login</Link>
+							<Link to="login">Login</Link> (
+							<Link to="login-fetcher">with useFetcher</Link>)
 						</li>
 						<li>
 							<Link to="todos">Todo list</Link>

examples/remix/app/routes/login-fetcher.tsx

@@ -0,0 +1,115 @@
+import { conform, parse, useForm } from '@conform-to/react';
+import type { ActionArgs } from '@remix-run/node';
+import { json } from '@remix-run/node';
+import { useFetcher } from '@remix-run/react';
+
+interface SignupForm {
+	email: string;
+	password: string;
+	confirmPassword: string;
+}
+
+function parseFormData(formData: FormData) {
+	return parse<SignupForm>(formData, {
+		resolve({ email, password, confirmPassword }) {
+			const error: Record<string, string> = {};
+
+			if (!email) {
+				error.email = 'Email is required';
+			} else if (!email.includes('@')) {
+				error.email = 'Email is invalid';
+			}
+
+			if (!password) {
+				error.password = 'Password is required';
+			}
+
+			if (!confirmPassword) {
+				error.confirmPassword = 'Confirm password is required';
+			} else if (confirmPassword !== password) {
+				error.confirmPassword = 'Password does not match';
+			}
+
+			if (error.email || error.password || error.confirmPassword) {
+				return { error };
+			}
+
+			// Return the value only if no error
+			return {
+				value: {
+					email,
+					password,
+					confirmPassword,
+				},
+			};
+		},
+	});
+}
+
+export async function action({ request }: ActionArgs) {
+	const formData = await request.formData();
+	const submission = parseFormData(formData);
+
+	/**
+	 * Signup only when the user click on the submit button and no error found
+	 */
+	if (!submission.value || submission.intent !== 'submit') {
+		// Always sends the submission state back to client until the user is signed up
+		return json({
+			...submission,
+			payload: {
+				// Never send the password back to client
+				email: submission.payload.email,
+			},
+		});
+	}
+
+	throw new Error('Not implemented');
+}
+
+export default function Signup() {
+	const fetcher = useFetcher<typeof action>();
+	// Last submission returned by the server
+	const lastSubmission = fetcher.data;
+	const [form, { email, password, confirmPassword }] = useForm({
+		// Sync the result of last submission
+		lastSubmission,
+
+		// Reuse the validation logic on the client
+		onValidate({ formData }) {
+			return parseFormData(formData);
+		},
+	});
+
+	return (
+		<fetcher.Form method="post" {...form.props}>
+			<div className="form-error">{form.error}</div>
+			<div>
+				<label>Email</label>
+				<input
+					className={email.error ? 'error' : ''}
+					{...conform.input(email)}
+				/>
+				<div>{email.error}</div>
+			</div>
+			<div>
+				<label>Password</label>
+				<input
+					className={password.error ? 'error' : ''}
+					{...conform.input(password, { type: 'password' })}
+				/>
+				<div>{password.error}</div>
+			</div>
+			<div>
+				<label>Confirm Password</label>
+				<input
+					className={confirmPassword.error ? 'error' : ''}
+					{...conform.input(confirmPassword, { type: 'password' })}
+				/>
+				<div>{confirmPassword.error}</div>
+			</div>
+			<hr />
+			<button type="submit">Signup</button>
+		</fetcher.Form>
+	);
+}