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React Native Academy · Lección

Escritura de hooks personalizados

Extraiga la lógica con estado a un hook personalizado reutilizable, compártalo entre dos componentes y siga la convención de nombres y las reglas de los hooks.

Escritura de hooks personalizados es una lección gratuita de React Native Academy en CoddyKit. Esta es la lección 4 de 4. Puedes leer la lección completa abajo gratuitamente — luego la practicas en el navegador con un editor de código integrado y un tutor de IA 24/7. Forma parte de la ruta de aprendizaje de React Native Academy, y tu progreso se sincroniza en la web y la app de CoddyKit. El curso de React Native Academy incluye 4 lecciones en total.

Partes de esta lección aún no han sido traducidas y se muestran en inglés.

What Are Custom Hooks?

Custom hooks are JavaScript functions whose names start with use and that may call other React hooks inside them. They let you extract stateful logic from a component into a reusable function. The logic is shared, but each component that calls the custom hook gets its own isolated state — custom hooks are not singletons.

The Rules of Hooks Apply to Custom Hooks

Custom hooks follow the same rules as built-in hooks: only call hooks at the top level (not inside loops or conditions), and only call hooks from React function components or other custom hooks. The use naming prefix is required — it signals to React and linters that the function follows these rules.

// Valid custom hook — starts with 'use'
function useCounter(initialValue) {
  const [count, setCount] = useState(initialValue);
  const increment = () => setCount(c => c + 1);
  const decrement = () => setCount(c => c - 1);
  const reset = () => setCount(initialValue);
  return { count, increment, decrement, reset };
}

A useCounter Custom Hook

The useCounter hook encapsulates a counter's state and its increment, decrement, and reset actions. Any component that needs a counter can call useCounter without repeating the state management logic. Each call to the hook creates an independent counter.

function CounterScreen() {
  const { count, increment, decrement, reset } = useCounter(0);

  return (
    <View>
      <Text>Count: {count}</Text>
      <Button title='+' onPress={increment} />
      <Button title='-' onPress={decrement} />
      <Button title='Reset' onPress={reset} />
    </View>
  );
}

A useFetch Custom Hook

A useFetch hook wraps the common pattern of fetching data with useEffect: it manages loading, data, and error states internally, and exposes them to the component. The URL is a dependency — changing it re-triggers the fetch.

function useFetch(url) {
  const [data, setData] = useState(null);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(null);

  useEffect(() => {
    setLoading(true);
    fetch(url)
      .then((res) => res.json())
      .then((json) => { setData(json); setLoading(false); })
      .catch((err) => { setError(err); setLoading(false); });
  }, [url]);

  return { data, loading, error };
}

Using the useFetch Hook

Components using useFetch become dramatically simpler. The component only describes what to render for each state (loading, error, data) without managing any fetch logic itself. If the same endpoint is needed in another screen, just call useFetch again — no code duplication.

function PostsScreen() {
  const { data, loading, error } = useFetch('https://jsonplaceholder.typicode.com/posts');

  if (loading) return <ActivityIndicator />;
  if (error) return <Text>Error: {error.message}</Text>;

  return (
    <FlatList
      data={data}
      keyExtractor={(item) => String(item.id)}
      renderItem={({ item }) => <Text>{item.title}</Text>}
    />
  );
}

A useToggle Custom Hook

A useToggle hook simplifies managing boolean state that needs to switch between true and false. It is useful for modals, accordions, dark mode, or any feature that toggles. The hook returns the current value and a stable toggle function.

function useToggle(initialValue = false) {
  const [value, setValue] = useState(initialValue);
  const toggle = useCallback(() => setValue((v) => !v), []);
  return [value, toggle];
}

// Usage
const [isVisible, toggleVisible] = useToggle(false);
<Button title='Show/Hide' onPress={toggleVisible} />
<Modal visible={isVisible} ... />

A useForm Custom Hook

A useForm hook manages a form's field values, change handler, and reset action. This pattern eliminates boilerplate in forms across the app. The hook accepts an object of initial field values and returns the current values, a generic field change handler, and a reset function.

function useForm(initialValues) {
  const [values, setValues] = useState(initialValues);

  const handleChange = useCallback((field, value) => {
    setValues((prev) => ({ ...prev, [field]: value }));
  }, []);

  const reset = useCallback(() => setValues(initialValues), [initialValues]);

  return { values, handleChange, reset };
}

A useNetworkStatus Custom Hook

A useNetworkStatus hook wraps the NetInfo API to expose the device's online/offline status. Components can simply read the boolean value without knowing about event subscription setup and teardown — the hook handles that internally with a useEffect cleanup function.

import NetInfo from '@react-native-community/netinfo';

function useNetworkStatus() {
  const [isOnline, setIsOnline] = useState(true);

  useEffect(() => {
    const unsubscribe = NetInfo.addEventListener((state) => {
      setIsOnline(state.isConnected ?? true);
    });
    return unsubscribe; // cleanup on unmount
  }, []);

  return isOnline;
}

Sharing Logic Between Components

The real power of custom hooks is sharing logic, not UI. Two screens can both call useNetworkStatus and each gets its own subscription. If the hook has a side effect (like a subscription), it is automatically cleaned up when the component using it unmounts. Each component's hook instance is fully independent.

// Both screens share the same logic, not the same state
function HomeScreen() {
  const isOnline = useNetworkStatus();
  return <Text>{isOnline ? 'Online' : 'Offline'}</Text>;
}

function ProfileScreen() {
  const isOnline = useNetworkStatus(); // independent subscription
  return <Banner visible={!isOnline} message='No connection' />;
}

Custom Hook Naming and Organization

Name custom hooks descriptively: useAuth, useCart, useDebounce, useWindowDimensions. Store hooks in a dedicated hooks/ directory to keep them organized and findable. Each hook should have a single clear responsibility — avoid creating hooks that do five unrelated things.

// Project structure
src/
  hooks/
    useAuth.js
    useFetch.js
    useForm.js
    useToggle.js
    useNetworkStatus.js

A useDebounce Custom Hook

A useDebounce hook delays propagating a value until a specified time has passed since the last update. This is perfect for search inputs where you want to wait until the user stops typing before firing an API request. The hook uses useEffect and a timer to manage the delay.

function useDebounce(value, delay) {
  const [debouncedValue, setDebouncedValue] = useState(value);

  useEffect(() => {
    const timer = setTimeout(() => {
      setDebouncedValue(value);
    }, delay);
    return () => clearTimeout(timer);
  }, [value, delay]);

  return debouncedValue;
}

// Usage
const debouncedQuery = useDebounce(searchQuery, 400);
useEffect(() => { fetchResults(debouncedQuery); }, [debouncedQuery]);

Quick Check

Test your understanding of writing custom hooks from this lesson.

Lesson Recap

In this lesson you learned: custom hooks are functions starting with 'use' that encapsulate stateful logic, each component calling a custom hook gets its own independent state and effects, and organize hooks in a dedicated hooks/ directory for a single responsibility per hook. Next up we explore the Context API for sharing global state without prop drilling.

Preguntas frecuentes

¿La lección «Escritura de hooks personalizados» es gratis?

Sí — el texto completo de «Escritura de hooks personalizados» es gratis para leer aquí en la web. Para practicarla de forma interactiva (editor de código integrado y tutor de IA 24/7) y desbloquear el resto del curso de React Native Academy, actualiza a CoddyKit PRO. El curso de React Native Academy incluye 4 lecciones en total.

¿Qué aprenderé en «Escritura de hooks personalizados»?

Extraiga la lógica con estado a un hook personalizado reutilizable, compártalo entre dos componentes y siga la convención de nombres y las reglas de los hooks. Practicas React Native Academy con código real que ejecutas directamente en el navegador, y un tutor de IA 24/7 responde tus preguntas mientras trabajas en la lección.

¿Necesito experiencia previa para empezar React Native Academy?

No se requiere experiencia previa. React Native Academy en CoddyKit está estructurado para principiantes hasta estudiantes avanzados, así que puedes empezar aquí o desde el inicio y avanzar a tu ritmo. Esta es la lección 4 de 4.

¿Cuánto tiempo toma la lección «Escritura de hooks personalizados»?

La mayoría de las lecciones de CoddyKit toman alrededor de 5–10 minutos. Cada una es compacta e interactiva, así que avanzas constantemente y retomas exactamente por donde dejaste en la web y la app.

¿Puedo escribir y ejecutar código en esta lección de React Native Academy?

Sí. Cada lección de React Native Academy incluye un editor de código integrado, así que escribes y ejecutas código real directamente en tu navegador y obtienes retroalimentación instantánea de IA — sin configuración local necesaria.

Todas las lecciones de este curso

  1. useRef para nodos DOM y valores mutables
  2. useReducer para lógica de estado compleja
  3. useCallback y useMemo para el rendimiento
  4. Escritura de hooks personalizados
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