Build & App Store

Development vs Production Build

During development, you run the app through Expo Go — a shell app that loads your JavaScript code over the network. This is fast for iteration but not distributable. For the App Store, you need a standalone binary — a real .ipa (iOS) or .apk/.aab (Android) file.

EAS Build

Install the EAS CLI and configure your project:

# Install EAS CLI globally
npm install -g eas-cli

# Log in to your Expo account
eas login

# Initialize EAS in your project
cd apps/expo && eas build:configure

This creates an eas.json file with build profiles:

{
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal"
    },
    "preview": {
      "distribution": "internal"
    },
    "production": {}
  }
}

To build for a specific platform:

# Build for iOS
eas build --platform ios

# Build for Android
eas build --platform android

# Build for both
eas build --platform all

iOS Build

Building for iOS requires an Apple Developer account ($99/year). Apple requires all iOS apps to be signed with certificates and provisioning profiles. EAS handles this automatically — it creates and manages certificates for you.

Requirements for an iOS build:

• Apple Developer account ($99/year)
• App ID registered in Apple Developer portal (EAS does this automatically)
• Signing certificates and provisioning profiles (EAS manages these)
• Bundle identifier (e.g., com.yourcompany.fitness)

# Build for iOS production
eas build --platform ios --profile production

# Submit to App Store Connect (TestFlight)
eas submit --platform ios

Android Build

Android builds require a signing keystore — a file that proves you are the developer of the app. EAS can generate one for you automatically on your first build.

# Build an APK (for direct sharing/testing)
eas build --platform android --profile preview

# Build an AAB (for Play Store submission)
eas build --platform android --profile production

# Submit to Google Play Store
eas submit --platform android

For the Play Store, you need a Google Play Developer account ($25 one-time fee). Unlike Apple, the Android build process works on any operating system.

App Store Assets

Both the Apple App Store and Google Play Store require specific assets before you can publish your app:

OTA Updates

OTA updates are one of the biggest advantages of React Native with Expo. App Store review can take 1-3 days. With OTA, your fix reaches users in minutes.

# Push an OTA update to all users on the production channel
eas update --branch production --message "Fix workout timer bug"

# Push to a preview channel for testing first
eas update --branch preview --message "Test new feature"

There are important limitations to OTA updates:

• Can update: JavaScript code, images, fonts — anything in the JS bundle
• ✕ Cannot update: Native code, new native modules, app icon, splash screen

Deploying the API

Your mobile app needs a live API to talk to. During development, the app connects tolocalhost. In production, it connects to your deployed API server.

Deploy the Go API using grit deploy (covered in the Grit Web Deploy course) to a VPS with a domain and HTTPS. Then update the mobile app's API URL:

// lib/api.ts
const API_URL = __DEV__
  ? "http://localhost:8080"       // Development
  : "https://api.fitness.com"     // Production

The __DEV__ variable is true in development and false in production builds. This lets you switch between local and remote APIs automatically.

Summary

Here's what you learned in this course:

• EAS Build compiles your app in the cloud — no Xcode or Android Studio needed
• iOS requires an Apple Developer account; Android requires a Google Play Developer account
• TestFlight distributes iOS betas; APKs distribute Android test builds directly
• OTA updates ship JS changes instantly — no store review required
• Deploy the Go API to a VPS with HTTPS for production mobile apps