提交与重置表单
使用 handleSubmit 处理表单提交，使用经过验证的值发起 API 请求，显示成功消息或服务器错误消息，并在成功后重置表单。
提交与重置表单 是 CoddyKit 上的免费 React Native Academy 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 React Native Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 React Native Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
The handleSubmit Wrapper
handleSubmit from useForm is a higher-order function that wraps your submit handler. When called, it first runs all validation rules. If every field passes, it calls your handler with the typed form data. If any field fails, it populates formState.errors and does not call your handler. Never read form values directly from state inside the submit handler — always use the typed data argument that handleSubmit provides.
const { handleSubmit } = useForm<LoginForm>();
async function onSubmit(data: LoginForm) {
// data is fully typed — guaranteed to have passed validation
console.log(data.email, data.password);
await authApi.login(data.email, data.password);
}
// Wire to button:
<Button title='Log In' onPress={handleSubmit(onSubmit)} />Making an API Call in the Submit Handler
The submit handler is an async function — handleSubmit handles the Promise automatically. Make your API call inside a try-catch block. On success, navigate to the next screen or show a success message. On failure, use setError to show a field-level error or display a general error with Alert.
async function onSubmit(data: RegisterForm) {
try {
await api.register({
email: data.email,
password: data.password,
name: data.name,
});
navigation.replace('Home');
} catch (err: any) {
if (err.status === 409) {
setError('email', { message: 'This email is already in use.' });
} else {
Alert.alert('Registration Failed', 'Please try again later.');
}
}
}isSubmitting to Block Double Submissions
formState.isSubmitting is automatically set to true while your async submit handler is running and to false when it completes. Use it to disable the submit button during the API call. Without this guard, fast double-taps can submit the form twice, causing duplicate records on the server or charging a user twice.
const { handleSubmit, formState: { isSubmitting } } = useForm<LoginForm>();
return (
<View>
{/* ... form fields ... */}
<TouchableOpacity
onPress={handleSubmit(onSubmit)}
disabled={isSubmitting}
style={[styles.button, isSubmitting && styles.buttonDisabled]}
>
{isSubmitting
? <ActivityIndicator color='white' />
: <Text style={styles.buttonText}>Log In</Text>
}
</TouchableOpacity>
</View>
);Handling Submission Errors from the Server
When the server returns a general error (not tied to a specific field), display it near the submit button or in an error banner above the form. Use a local serverError state variable that you set in the catch block. This separates server-level errors from field-level validation errors and gives users a clear message about what went wrong.
const [serverError, setServerError] = React.useState<string | null>(null);
async function onSubmit(data: LoginForm) {
setServerError(null); // clear previous error
try {
await api.login(data);
navigation.replace('Dashboard');
} catch {
setServerError('Login failed. Please check your credentials.');
}
}
// In render:
{serverError && (
<Text style={styles.serverError}>{serverError}</Text>
)}Showing a Success State
After a successful submission, provide clear feedback before navigating away. An inline success message, a check-mark animation, or a brief delay before navigation all help users feel confident the action completed. For forms like contact or feedback submission that do not navigate away, reset the form and show a success banner in place of the submit button.
const [submitted, setSubmitted] = React.useState(false);
async function onSubmit(data: FeedbackForm) {
await api.sendFeedback(data);
setSubmitted(true);
reset();
}
if (submitted) {
return (
<View style={styles.success}>
<Ionicons name='checkmark-circle' size={64} color='green' />
<Text>Thank you! Your feedback was sent.</Text>
</View>
);
}Resetting to Default Values
Call reset() with no arguments to clear all fields back to their defaultValues and also clear all errors. This is useful for 'Send Another' flows where the user wants to submit the same form type multiple times, or for forms that appear in a modal and need to be blank when reopened. The reset is synchronous and immediate.
const { reset } = useForm<ContactForm>({
defaultValues: { name: '', email: '', message: '' },
});
async function onSubmit(data: ContactForm) {
await api.sendMessage(data);
reset(); // all fields cleared, errors cleared
Alert.alert('Sent!', 'Your message has been delivered.');
}Resetting to New Values
Pass a value object to reset(newValues) to replace the default values and repopulate the form at the same time. This is the correct way to pre-fill an edit form with data loaded from the server. Call reset inside a useEffect that runs when the server data arrives to populate all fields without triggering field-level validation.
const { reset } = useForm<ProfileForm>();
useEffect(() => {
if (userProfile) {
reset({
name: userProfile.name,
bio: userProfile.bio,
website: userProfile.website ?? '',
});
}
}, [userProfile, reset]);Resetting Individual Fields with setValue
Sometimes you only want to reset or update one specific field without clearing the entire form. Use setValue(fieldName, newValue) for targeted updates. An optional third argument { shouldValidate: true } re-runs validation for that field after the value is set, useful when you programmatically change a field and want errors to update immediately.
const { setValue } = useForm<AddressForm>();
async function handleLocationPress() {
const loc = await Location.getCurrentPositionAsync({});
const [address] = await Location.reverseGeocodeAsync(loc.coords);
setValue('city', address.city ?? '', { shouldValidate: true });
setValue('postalCode', address.postalCode ?? '');
}isDirty and Unsaved Changes Guard
formState.isDirty is true when any field value differs from its default value. Use this to warn the user before they navigate away from an unsaved form. Hook into navigation's beforeRemove event (React Navigation) to show a 'Discard changes?' alert when the form is dirty and the user tries to go back.
const { formState: { isDirty } } = form;
useEffect(() => {
const unsubscribe = navigation.addListener('beforeRemove', (e) => {
if (!isDirty) return;
e.preventDefault();
Alert.alert('Discard changes?', 'You have unsaved changes.', [
{ text: 'Keep Editing', style: 'cancel' },
{ text: 'Discard', style: 'destructive',
onPress: () => navigation.dispatch(e.data.action) },
]);
});
return unsubscribe;
}, [navigation, isDirty]);Validating on Demand with trigger
You can call trigger() with no arguments to validate all fields at any time — not just on submit. Call it when the user taps a 'Check' button, when they reach the end of a scrollable form, or to pre-validate before switching tabs. This is useful for showing all errors at once so users can fix everything before hitting the submit button.
const { trigger, formState: { errors } } = useForm<RegisterForm>();
async function handleCheckAll() {
const isValid = await trigger();
if (!isValid) {
Alert.alert('Please fix the highlighted fields before submitting.');
}
}Complete Login Form Example
Here is a production-ready login form combining everything from this lesson: typed useForm, Controller-wrapped inputs, validation rules, isSubmitting guard, server error display, and navigation on success. This template can be adapted for any authentication or data entry screen in a React Native app.
export default function LoginScreen() {
const { control, handleSubmit, formState: { errors, isSubmitting } } = useForm<LoginForm>();
const [serverError, setServerError] = React.useState<string | null>(null);
async function onSubmit(data: LoginForm) {
setServerError(null);
try {
await authApi.login(data.email, data.password);
navigation.replace('Home');
} catch { setServerError('Invalid credentials.'); }
}
return (
<View style={styles.container}>
{serverError && <Text style={styles.serverError}>{serverError}</Text>}
<EmailController control={control} error={errors.email} />
<PasswordController control={control} error={errors.password} />
<Button title={isSubmitting ? 'Logging in...' : 'Log In'}
onPress={handleSubmit(onSubmit)} disabled={isSubmitting} />
</View>
);
}Quick Check
Test your understanding of React Native Mobile Development concepts from this lesson.
Lesson Recap
In this lesson you learned: handleSubmit validates all fields before calling your async handler and sets isSubmitting automatically, reset() clears the form while reset(newValues) repopulates it for edit scenarios, and isDirty guards against accidental data loss by warning before navigation. Next we begin the B2 courses, starting with Supabase integration in React Native.
常见问题解答
「提交与重置表单」课时是免费的吗？
是的 — 「提交与重置表单」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 React Native Academy 课程的其余内容，请升级到 CoddyKit PRO。 React Native Academy 课程共包含 4 节课。
「提交与重置表单」这节课中我会学到什么？
使用 handleSubmit 处理表单提交，使用经过验证的值发起 API 请求，显示成功消息或服务器错误消息，并在成功后重置表单。 你通过在浏览器中直接运行的动手代码来练习 React Native Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 React Native Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 React Native Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「提交与重置表单」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 React Native Academy 课中编写并运行代码吗？
能。每节 React Native Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。