EAS Build (Expo) in React Native - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is EAS Build in Expo?

EAS Build is a service by Expo that helps you build your React Native app in the cloud, so you don't need to set up complicated build tools on your computer.

beginner

How does EAS Build improve the app development process?

It saves time by building apps on powerful servers, handles native code compilation, and lets you get ready-to-publish app files without managing local build environments.

intermediate

What file do you configure to customize EAS Build settings?

You use the eas.json file in your project root to set build profiles and options for EAS Build.

beginner

What command starts a build with EAS Build?

You run eas build --platform ios or eas build --platform android in your terminal to start building your app for iOS or Android.

intermediate

Why is EAS Build useful for teams working on React Native apps?

Because it provides consistent builds for everyone, avoids local setup issues, and speeds up the process by using cloud servers.

What does EAS Build do?

A Runs your app on a device

B Creates app UI components

C Builds your app in the cloud

D Publishes your app to stores automatically

EAS Build compiles your app in the cloud, not runs or publishes it automatically.

Which file configures EAS Build settings?

A build.config

B package.json

C app.json

D eas.json

The eas.json file is used to set build profiles and options.

How do you start an Android build with EAS?

A eas build --platform android

B expo start android

C npm run build-android

D eas start android

The correct command is eas build --platform android.

Which is NOT a benefit of EAS Build?

A Automatic app publishing to stores

B Faster builds using cloud servers

C Consistent builds for teams

D No local build setup needed

EAS Build does not automatically publish apps to stores.

EAS Build is part of which ecosystem?

A React Native CLI

B Expo

C Flutter

D Android Studio

EAS Build is a service provided by Expo for React Native apps.

Explain how EAS Build helps simplify building React Native apps.

Think about how building apps locally can be tricky and how EAS Build changes that.

Describe the role of the eas.json file in EAS Build.

Consider where you tell EAS Build how to build your app.

Practice

1. What is the main purpose of eas build in Expo?

easy

A. To publish the app directly to app stores

B. To run the app on a local simulator

C. To build app files for Android and iOS in the cloud

D. To create a new Expo project

Solution

1. Step 1: Understand the role of eas build

   The eas build command is used to create app binaries for Android and iOS using cloud services.

2. Step 2: Differentiate from other commands

   It does not run the app locally, publish directly, or create projects; it only builds app files.

3. Final Answer:

   To build app files for Android and iOS in the cloud -> Option C

4. Quick Check:

   EAS Build = cloud app file creation [OK]

Hint: Remember: eas build creates app files remotely [OK]

Common Mistakes:

• Confusing build with running the app locally
• Thinking it publishes directly to stores
• Assuming it creates new projects

2. Which of the following is the correct syntax to start a build for Android using EAS?

easy

A. eas build --device android

B. eas build android --platform

C. eas build -p ios

D. eas build --platform android

Solution

1. Step 1: Identify the correct command format

   The correct syntax uses eas build --platform android to specify the platform.

2. Step 2: Check other options for errors

   eas build --device android uses invalid flag, eas build android --platform has wrong syntax order, eas build -p ios targets iOS.

3. Final Answer:

   eas build --platform android -> Option D

4. Quick Check:

   Correct flag for platform is --platform [OK]

Hint: Use --platform flag followed by platform name [OK]

Common Mistakes:

• Mixing up flag order
• Using wrong flags like --device
• Confusing platform names

3. What will happen if you run eas build --platform ios --profile production?

medium

A. It builds an iOS app using the production profile in the cloud

B. It builds an Android app using the production profile

C. It runs the app on an iOS simulator locally

D. It creates a new production profile

Solution

1. Step 1: Analyze the command flags

   The command specifies --platform ios and --profile production, meaning it builds for iOS using the production profile.

2. Step 2: Understand the build behavior

   EAS Build runs in the cloud and does not run simulators or create profiles with this command.

3. Final Answer:

   It builds an iOS app using the production profile in the cloud -> Option A

4. Quick Check:

   Platform + profile flags define build target [OK]

Hint: Platform and profile flags control build target and config [OK]

Common Mistakes:

• Assuming it runs locally
• Confusing platform with Android
• Thinking it creates profiles

4. You run eas build --platform android --profile staging but get an error saying the profile is missing. What is the likely cause?

medium

A. You used the wrong platform flag

B. The staging profile is not defined in eas.json

C. You need to run expo start first

D. Your internet connection is off

Solution

1. Step 1: Understand profile usage in EAS Build

   Profiles like staging must be defined in the eas.json file to be used.

2. Step 2: Check other options for relevance

   Platform flag is correct, expo start is unrelated, and internet issues cause different errors.

3. Final Answer:

   The staging profile is not defined in eas.json -> Option B

4. Quick Check:

   Missing profile in config causes build error [OK]

Hint: Check eas.json for profile definitions before building [OK]

Common Mistakes:

• Ignoring eas.json profiles
• Confusing build with running app
• Assuming network error

5. You want to share your app with testers before publishing. Which EAS Build feature helps you do this easily?

hard

A. Using eas build to create app files and share build URLs

B. Running expo publish to update the app instantly

C. Using expo start to open the app on testers' devices

D. Creating a new Expo project with expo init

Solution

1. Step 1: Identify how EAS Build supports sharing

   EAS Build creates app binaries and provides URLs to share with testers easily.

2. Step 2: Differentiate from other Expo commands

   expo publish updates JS bundles but not native builds; expo start is for development; expo init creates projects.

3. Final Answer:

   Using eas build to create app files and share build URLs -> Option A

4. Quick Check:

   EAS Build creates shareable app files [OK]

Hint: Build app files and share URLs with testers using EAS Build [OK]

Common Mistakes:

• Confusing publishing with building
• Thinking expo start shares apps
• Assuming new project creation helps sharing