React Native

React Native Skill

Project Structure

project/
 src/
    core/                   # Pure business logic (no React)
       types.ts
       services/
    components/             # Reusable UI components
       Button/
          Button.tsx
          Button.test.tsx
          index.ts
       index.ts            # Barrel export
    screens/                # Screen components
       Home/
          HomeScreen.tsx
          useHome.ts      # Screen-specific hook
          index.ts
       index.ts
    navigation/             # Navigation configuration
    hooks/                  # Shared custom hooks
    store/                  # State management
    utils/                  # Utilities
 __tests__/
 android/
 ios/
 CLAUDE.md

Component Patterns

Functional Components Only

// Good - simple, testable
interface ButtonProps {
  label: string;
  onPress: () => void;
  disabled?: boolean;
}

export function Button({ label, onPress, disabled = false }: ButtonProps): JSX.Element {
  return (
    <Pressable disabled={disabled}>
      <Text>{label}</Text>
    </Pressable>
  );
}

Extract Logic to Hooks

// useHome.ts - all logic here
export function useHome() {
  const [items, setItems] = useState<Item[]>([]);
  const [loading, setLoading] = useState(false);

  const refresh = useCallback(async () => {
    setLoading(true);
    const data = await fetchItems();
    setItems(data);
    setLoading(false);
  }, []);

  return { items, loading, refresh };
}

// HomeScreen.tsx - pure presentation
export function HomeScreen(): JSX.Element {
  const { items, loading, refresh } = useHome();

  return (
    <ItemList items={items} loading={loading} />
  );
}

Props Interface Always Explicit

// Always define props interface, even if simple
interface ItemCardProps {
  item: Item;
  onPress: (id: string) => void;
}

export function ItemCard({ item, onPress }: ItemCardProps): JSX.Element {
  ...
}

State Management

Local State First

// Start with useState, escalate only when needed
const [value, setValue] = useState('');

Zustand for Global State (if needed)

// store/useAppStore.ts
import { create } from 'zustand';

interface AppState {
  user: User | null;
  setUser: (user: User | null) => void;
}

export const useAppStore = create<AppState>((set) => ({
  user: null,
  setUser: (user) => set({ user }),
}));

React Query for Server State

// hooks/useItems.ts
import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';

export function useItems() {
  return useQuery({
    queryKey: ['items'],
    queryFn: fetchItems,
  });
}

export function useCreateItem() {
  const queryClient = useQueryClient();

  return useMutation({
    mutationFn: createItem,
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['items'] });
    },
  });
}

Testing

Component Testing with React Native Testing Library

import { render, fireEvent } from '@testing-library/react-native';
import { Button } from './Button';

describe('Button', () => {
  it('calls onPress when pressed', () => {
    const
    const { getByText } = render(<Button label="Click me" />);

    fireEvent.press(getByText('Click me'));

    expect(onPress).toHaveBeenCalledTimes(1);
  });

  it('does not call onPress when disabled', () => {
    const
    const { getByText } = render(<Button label="Click me" disabled />);

    fireEvent.press(getByText('Click me'));

    expect(onPress).not.toHaveBeenCalled();
  });
});

Hook Testing

import { renderHook, act } from '@testing-library/react-hooks';
import { useCounter } from './useCounter';

describe('useCounter', () => {
  it('increments counter', () => {
    const { result } = renderHook(() => useCounter());

    act(() => {
      result.current.increment();
    });

    expect(result.current.count).toBe(1);
  });
});

Platform-Specific Code

Use Platform.select Sparingly

import { Platform } from 'react-native';

const styles = StyleSheet.create({
  shadow: Platform.select({
    ios: {
      shadowColor: '#000',
      shadowOffset: { width: 0, height: 2 },
      shadowOpacity: 0.1,
    },
    android: {
      elevation: 2,
    },
  }),
});

Separate Files for Complex Differences

Component/
 Component.tsx          # Shared logic
 Component.ios.tsx      # iOS-specific
 Component.android.tsx  # Android-specific
 index.ts

React Native Anti-Patterns

• Inline styles - use StyleSheet.create
• Logic in render - extract to hooks
• Deep component nesting - flatten hierarchy
• Anonymous functions in props - use useCallback
• Index as key in lists - use stable IDs
• Direct state mutation - always use setter
• Mixing business logic with UI - keep core/ pure
• Ignoring TypeScript errors - fix them
• Large components - split into smaller pieces

Source: EmmanuelOrtiz87/gentle-vanguard — distributed by TomeVault.