Expo Patterns

Expo Mobile Patterns

Complete guide for building beautiful cross-platform mobile apps with Expo. Combines official Expo skills with foundational patterns.

Running the App

CRITICAL: Always try Expo Go first before creating custom builds.

Most Expo apps work in Expo Go without any custom native code.

npx expo start  # Scan QR with Expo Go

When Custom Builds Are Required

You need npx expo run:ios/android or eas build ONLY when using:

• Local Expo modules (custom native code in modules/)
• Apple targets (widgets, app clips via @bacons/apple-targets)
• Third-party native modules not in Expo Go
• Custom native configuration

Core Stack

Context7 Library IDs

Query these for current best practices:

• Expo: expo
• React Native: /facebook/react-native
• Better Auth: /better-auth/better-auth

Library Preferences

Code Style

• Always use kebab-case for file names: comment-card.tsx
• Routes belong in the app directory only
• Never co-locate components in the app directory
• Configure tsconfig.json with path aliases
• Ensure app always has a route matching "/"

Native Tabs (SDK 54+)

Always prefer NativeTabs from expo-router/unstable-native-tabs:

import { NativeTabs, Icon, Label, Badge } from "expo-router/unstable-native-tabs";

export default function TabLayout() {
  return (
    <NativeTabs minimizeBehavior="onScrollDown">
      <NativeTabs.Trigger name="index">
        <Label>Home</Label>
        <Icon sf="house.fill" />
        <Badge>9+</Badge>
      </NativeTabs.Trigger>
      <NativeTabs.Trigger name="settings">
        <Icon sf="gear" />
        <Label>Settings</Label>
      </NativeTabs.Trigger>
      <NativeTabs.Trigger name="(search)" role="search">
        <Label>Search</Label>
      </NativeTabs.Trigger>
    </NativeTabs>
  );
}

NativeTabs Rules

• Include a trigger for each tab
• name must match route name exactly (including parentheses)
• Place search tab last to combine with search bar
• Use role prop: search, favorites, more, etc.

Icon Component

<Icon sf="house.fill" />                              // SF Symbol only
<Icon sf="house.fill" drawable="ic_home" />           // With Android drawable
<Icon src={require('./icon.png')} />                  // Custom image
<Icon sf={{ default: "house", selected: "house.fill" }} /> // State variants

SF Symbols (expo-symbols)

Use SF Symbols for native feel. Never use FontAwesome or Ionicons.

import { SymbolView } from "expo-symbols";
import { PlatformColor } from "react-native";

<SymbolView
  tintColor={PlatformColor("label")}
  resizeMode="scaleAspectFit"
  name="square.and.arrow.down"
  style={{ width: 16, height: 16 }}
/>

Common Icons

Animated Symbols

<SymbolView
  name="checkmark.circle"
  animationSpec={{ effect: { type: "bounce", direction: "up" } }}
/>

Effects: bounce, pulse, variableColor, scale

Expo Router Navigation

Basic Layouts

// app/_layout.tsx - Root layout with Stack
import { Stack } from 'expo-router';
export default function RootLayout() {
  return <Stack />;
}

// app/(tabs)/_layout.tsx - Tab navigation
import { Tabs } from 'expo-router';
export default function TabLayout() {
  return <Tabs />;
}

Link Navigation

import { Link, router } from 'expo-router';

// Declarative
<Link href="/profile">Go to Profile</Link>

// With custom component
<Link href="/path" asChild>
  <Pressable>...</Pressable>
</Link>

// Programmatic
router.push('/settings');
router.replace('/home');
router.back();

Link Previews & Context Menus

<Link href="/settings">
  <Link.Trigger>
    <Pressable><Card /></Pressable>
  </Link.Trigger>
  <Link.Preview />
  <Link.Menu>
    <Link.MenuAction title="Share" icon="square.and.arrow.up" />
    <Link.MenuAction title="Delete" icon="trash" destructive />
  </Link.Menu>
</Link>

Modal & Sheet

// Modal
<Stack.Screen name="modal" options={{ presentation: "modal" }} />

// Sheet with liquid glass (iOS 26+)
<Stack.Screen
  name="sheet"
  options={{
    presentation: "formSheet",
    sheetGrabberVisible: true,
    sheetAllowedDetents: [0.5, 1.0],
    contentStyle: { backgroundColor: "transparent" },
  }}
/>

Dynamic Routes

// app/[id].tsx
import { useLocalSearchParams } from 'expo-router';
export default function Detail() {
  const { id } = useLocalSearchParams();
  return <View>...</View>;
}

Common Route Structure

app/
  _layout.tsx          — <NativeTabs />
  (index,search)/
    _layout.tsx        — <Stack />
    index.tsx          — Main list
    search.tsx         — Search view
    i/[id].tsx         — Detail view

Styling (Apple HIG)

• Prefer flex gap over margin/padding
• Inline styles, not StyleSheet.create (unless reusing)
• Use { borderCurve: 'continuous' } for rounded corners
• Use CSS boxShadow, NEVER legacy React Native shadow

<View style={{ boxShadow: "0 1px 2px rgba(0, 0, 0, 0.05)" }} />

Responsiveness

• Use <ScrollView contentInsetAdjustmentBehavior="automatic" /> instead of SafeAreaView
• Apply to FlatList and SectionList too
• Use flexbox, not Dimensions API
• ALWAYS prefer useWindowDimensions over Dimensions.get()

Text

• Add selectable prop for copyable data
• Use { fontVariant: 'tabular-nums' } for counters

Reanimated Animations

import Animated, { 
  useSharedValue, 
  useAnimatedStyle, 
  withSpring 
} from 'react-native-reanimated';

function AnimatedBox() {
  const offset = useSharedValue(0);
  
  const animatedStyles = useAnimatedStyle(() => ({
    transform: [{ translateX: withSpring(offset.value * 255) }],
  }));
  
  return <Animated.View style={[styles.box, animatedStyles]} />;
}

Gesture Handling

import { GestureDetector, Gesture } from 'react-native-gesture-handler';

function SwipeableCard() {
  const gesture = Gesture.Pan()
    .onUpdate((event) => {
      offset.value = event.translationX;
    })
    .onEnd(() => {
      offset.value = withSpring(0);
    });

  return (
    <GestureDetector gesture={gesture}>
      <Animated.View style={animatedStyles} />
    </GestureDetector>
  );
}

Visual Effects

// Blur
import { BlurView } from 'expo-blur';
<BlurView intensity={50} style={StyleSheet.absoluteFill} />

// Liquid Glass (iOS 26+)
import { GlassView } from 'expo-glass-effect';
<GlassView style={styles.glass} cornerRadius={16} />

Common Expo SDK Patterns

// Camera
import { CameraView, useCameraPermissions } from 'expo-camera';

// Notifications  
import * as Notifications from 'expo-notifications';

// Location
import * as Location from 'expo-location';

// Secure Storage
import * as SecureStore from 'expo-secure-store';

// Haptics (iOS)
import * as Haptics from 'expo-haptics';

// Splash Screen
import * as SplashScreen from 'expo-splash-screen';
SplashScreen.preventAutoHideAsync();
SplashScreen.hideAsync();

App Configuration

// app.config.ts
export default {
  expo: {
    name: "MyApp",
    slug: "my-app",
    version: "1.0.0",
    ios: {
      bundleIdentifier: "com.company.myapp",
      supportsTablet: true,
    },
    android: {
      package: "com.company.myapp",
      adaptiveIcon: {
        foregroundImage: "./assets/adaptive-icon.png",
        backgroundColor: "#ffffff"
      }
    },
    plugins: [
      "expo-router",
      ["expo-splash-screen", { backgroundColor: "#ffffff" }],
    ]
  }
};

EAS Build Configuration

// eas.json
{
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal",
      "ios": { "simulator": true }
    },
    "preview": {
      "distribution": "internal"
    },
    "production": {
      "autoIncrement": true
    }
  },
  "submit": {
    "production": {
      "ios": { "appleId": "...", "ascAppId": "..." },
      "android": { "track": "internal" }
    }
  }
}

Build Commands

npm install -g eas-cli && eas login

# Development build
eas build --platform ios --profile development
eas build --platform android --profile development

# Production build
eas build --platform all --profile production

# Submit to stores
eas submit --platform ios
eas submit --platform android

# OTA Update (no app store review!)
eas update --branch production --message "Bug fix"

Environment Variables

# .env (EXPO_PUBLIC_ prefix required)
EXPO_PUBLIC_API_URL=https://api.example.com

# Access in code
const apiUrl = process.env.EXPO_PUBLIC_API_URL;

# EAS environments
eas env:pull --environment development

Validation Commands

npx tsc --noEmit        # Type check
npx eslint .            # Lint
npm test                # Tests
npx expo-doctor         # Doctor check
npx expo start          # Start dev

Mobile Best Practices

• Expo Go first - only create custom builds when needed
• Use Expo Router for navigation (file-based, automatic deep linking)
• Respect platform conventions (iOS HIG, Material Design)
• 60fps animations with Reanimated worklets
• Handle safe areas with contentInsetAdjustmentBehavior="automatic"
• Use expo-haptics conditionally on iOS
• Offline-first with proper loading/error states
• Test on real devices via EAS internal distribution
• Accessibility - use accessibilityLabel, accessibilityRole
• OTA updates - use EAS Update for instant bug fixes