React Native Academy · Ders

Controller ile react-hook-form Kurulumu

react-hook-form paketini kurun, bir form örneği oluşturmak için useForm kullanın ve kaydetmek ve onChange/onBlur almak üzere her TextInput bileşenini bir Controller ile sarın.

Controller ile react-hook-form Kurulumu, CoddyKit'te ücretsiz bir React Native Academy dersidir. Bu, 4 dersinin 1. dersidir. Aşağıdan dersin tamamını ücretsiz okuyabilir, sonra tarayıcıda yerleşik kod editörü ve 7/24 yapay zeka koçu ile uygulamalı olarak pratik yapabilirsin. Bu, React Native Academy öğrenme yolunun bir parçasıdır ve ilerlemeniz web ve CoddyKit uygulaması arasında senkronize olur. React Native Academy kursu toplamda 4 dersten oluşur.

Bu dersin bazı bölümleri henüz çevrilmemiş olup İngilizce olarak gösterilmektedir.

Why react-hook-form?

react-hook-form is a performant, flexible library for building forms in React and React Native. Unlike manually wiring every input to useState, react-hook-form uses uncontrolled inputs to minimize re-renders. It integrates validation, error handling, and form submission into a single coherent API, and it works seamlessly with any UI component library through the Controller wrapper.

Installing react-hook-form

Install react-hook-form from npm. It has no dependencies and works with any React version 16.8+. No special configuration is needed — import its hooks and components directly into your React Native components after installation.

npm install react-hook-form

Creating a Form Instance with useForm

Call useForm() at the top of your component to create a form instance. It returns several utilities: control (for wiring inputs via Controller), handleSubmit (for form submission), formState.errors (for displaying validation errors), and reset (to clear all fields). Pass default values to useForm to pre-populate the form.

import { useForm } from 'react-hook-form';

interface LoginForm {
  email: string;
  password: string;
}

export default function LoginScreen() {
  const {
    control,
    handleSubmit,
    formState: { errors },
    reset,
  } = useForm<LoginForm>({
    defaultValues: { email: '', password: '' },
  });
}

Wrapping TextInput with Controller

In React Native, inputs are controlled components that need to be wrapped in Controller so react-hook-form can manage their values. Pass the control object, the field name, and a render prop. The render prop receives field which contains value, onChange, and onBlur to wire to the TextInput.

import { Controller } from 'react-hook-form';

<Controller
  control={control}
  name='email'
  render={({ field: { onChange, onBlur, value } }) => (
    <TextInput
      value={value}
      onChangeText={onChange}
      onBlur={onBlur}
      placeholder='Email'
      keyboardType='email-address'
      autoCapitalize='none'
    />
  )}
/>

Adding Validation Rules

Pass a rules prop to Controller to define validation constraints. The required rule marks a field as mandatory, minLength enforces a minimum character count, maxLength caps input length, and pattern validates against a regex. Each rule takes an object with a value and a message string shown when the rule fails.

<Controller
  control={control}
  name='email'
  rules={{
    required: { value: true, message: 'Email is required' },
    pattern: {
      value: /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/,
      message: 'Enter a valid email address',
    },
  }}
  render={({ field: { onChange, onBlur, value } }) => (
    <TextInput value={value} onChangeText={onChange} onBlur={onBlur} />
  )}
/>

Displaying Field Errors

After Controller validates a field, any error is available in formState.errors[fieldName]. Access its message property and render it below the input in a red Text component. Errors only appear after the field has been touched (onBlur) or after the first submit attempt, preventing premature error messages.

<Controller
  control={control}
  name='email'
  rules={{ required: 'Email is required' }}
  render={({ field: { onChange, onBlur, value } }) => (
    <View>
      <TextInput
        value={value}
        onChangeText={onChange}
        onBlur={onBlur}
        style={[styles.input, errors.email && styles.inputError]}
      />
      {errors.email && (
        <Text style={styles.errorText}>{errors.email.message}</Text>
      )}
    </View>
  )}
/>

Handling Form Submission with handleSubmit

Wrap your submit handler with handleSubmit. react-hook-form will run all validation rules first; if any field is invalid, it populates formState.errors and does not call your handler. If all fields are valid, your handler receives a typed object containing all field values — ready to send to an API.

async function onSubmit(data: LoginForm) {
  console.log('Submitting:', data.email, data.password);
  try {
    await authApi.login(data.email, data.password);
    navigation.replace('Home');
  } catch (err) {
    Alert.alert('Login Failed', 'Invalid email or password.');
  }
}

<Button title='Log In' onPress={handleSubmit(onSubmit)} />

Password Field Configuration

For password fields, set secureTextEntry to hide the typed characters and configure an appropriate keyboard type. Wire the field to Controller exactly like the email field. Many apps also add a 'show/hide' icon button that toggles secureTextEntry via local state — this improves accessibility for users with typos.

<Controller
  control={control}
  name='password'
  rules={{
    required: 'Password is required',
    minLength: { value: 8, message: 'Password must be at least 8 characters' },
  }}
  render={({ field: { onChange, onBlur, value } }) => (
    <TextInput
      value={value}
      onChangeText={onChange}
      onBlur={onBlur}
      secureTextEntry
      placeholder='Password'
    />
  )}
/>

Using watch to Observe Field Values

The watch function returned by useForm lets you subscribe to a field's current value and react to changes in real time. A common use case is a 'confirm password' field that validates its value matches the password field. Pass a field name to watch and use the returned value in the confirm field's validate rule.

const { control, handleSubmit, watch, formState: { errors } } = useForm<RegisterForm>();
const password = watch('password');

<Controller
  control={control}
  name='confirmPassword'
  rules={{
    validate: (value) =>
      value === password || 'Passwords do not match',
  }}
  render={({ field }) => <TextInput {...field} secureTextEntry />}
/>

Resetting the Form

Call reset() to clear all field values and errors, returning the form to its default values. You can also pass a new set of values to reset({ email: 'prefilled@example.com' }) to re-initialize the form with different defaults, which is useful for edit-profile forms that pre-populate with existing user data.

// Clear after successful submit:
async function onSubmit(data: LoginForm) {
  await api.login(data);
  reset(); // clears all inputs
}

// Pre-fill with existing profile data:
useEffect(() => {
  if (userProfile) {
    reset({
      name: userProfile.name,
      email: userProfile.email,
    });
  }
}, [userProfile]);

Form Validation Modes

react-hook-form offers several mode settings that control when validation runs: 'onSubmit' (default, validates only on submit), 'onBlur' (validates when a field loses focus), 'onChange' (validates on every keystroke), and 'all' (combines onBlur and onChange). For mobile forms, 'onBlur' offers the best balance between immediate feedback and avoiding distracting errors while typing.

const { control, handleSubmit } = useForm<LoginForm>({
  mode: 'onBlur',       // validate when user leaves a field
  defaultValues: { email: '', password: '' },
});

Quick Check

Test your understanding of React Native Mobile Development concepts from this lesson.

Lesson Recap

In this lesson you learned: useForm creates the form instance with control, handleSubmit, and formState.errors, Controller wires native TextInput components to the form with onChange, onBlur, and value props, and rules define built-in validation constraints that populate errors automatically. Next up we explore validation rules and error message handling in depth.

Sıkça Sorulan Sorular

“Controller ile react-hook-form Kurulumu” dersi ücretsiz mi?

Evet — “Controller ile react-hook-form Kurulumu” dersin tüm metni burada web'de ücretsiz olarak okunabilir. Etkileşimli olarak pratik yapmak (yerleşik kod editörü ve 7/24 yapay zeka koçu) ve React Native Academy kursunun geri kalanını açmak için CoddyKit PRO'ya yükselt. React Native Academy kursu toplamda 4 dersten oluşur.

“Controller ile react-hook-form Kurulumu” dersinde ne öğreneceğim?

react-hook-form paketini kurun, bir form örneği oluşturmak için useForm kullanın ve kaydetmek ve onChange/onBlur almak üzere her TextInput bileşenini bir Controller ile sarın. React Native Academy ile uygulamalı kodu tarayıcıda doğrudan çalıştırarak pratik yaparsın ve 7/24 yapay zeka koçu dersi çalışırken sorularını yanıtlar.

React Native Academy öğrenmeye başlamak için deneyim gerekli mi?

Önceden deneyim gerekmez. CoddyKit'te React Native Academy, başlangıçtan ileri seviyeye kadar yapılandırıldığı için buradan başlayabilir veya başından başlayıp kendi hızında ilerleme yapabilirsin. Bu, 4 dersinin 1. dersidir.

“Controller ile react-hook-form Kurulumu” dersi ne kadar sürer?

Çoğu CoddyKit dersi yaklaşık 5–10 dakika sürer. Her biri kısa ve etkileşimli olduğu için sabit ilerleme yaparsın ve web ile uygulama arasında tam olarak bıraktığın yerden devam edebilirsin.

Bu React Native Academy dersinde kod yazıp çalıştırabilir miyim?

Evet. Her React Native Academy dersi yerleşik bir kod editörü içerir, bu sayede tarayıcıda gerçek kod yazıp çalıştırabilir ve anlık yapay zeka geri bildirimi alırsın — yerel kurulum gerekli değildir.

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