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Configure a development build in cloud

Learn how to configure a development build for a project using EAS Build.

In this chapter, we'll set up and configure a development build with EAS for our example app.

Understanding development builds

Let's start by learning about what are development builds and why we need them.

A development build is a debug version of our project. It is optimized for quick iterations when creating an app. It contains the expo-dev-client library, which offers a robust and complete development environment. This setup allows us to integrate any native library or change code inside the native directories as required.

Key highlights

Note: If you are familiar with Expo Go, think of a development build as a customizable version of Expo Go that is unique to the requirements of a project.

FeatureDevelopment BuildsExpo Go
Development phaseOffers web-like iteration speed for mobile app development.Allows for quick iteration and testing of Expo SDK projects using the client app.
CollaborationFacilitates team testing with shared native runtime.Easy project sharing via QR codes on a device.
Third-party libraries supportFull support for any third-party library, including those that require custom native code.Limited to libraries within the Expo SDK, not suitable for custom native dependencies.
CustomizationExtensive customization with config plugins and direct access to native code.Limited customization with a focus on Expo SDK capabilities without direct native code modification.
Intended useIdeal for full-fledged app development aimed at store deployment, offering a complete development environment and tools.Ideal for learning, prototyping, and experimenting. Not recommended for production apps.

1

Install expo-dev-client library

To initialize our project for a development build, let's cd inside our project directory and run the following command to install the library:

Terminal
- npx expo install expo-dev-client

Start the development server

Run the npx expo start to start the development server:

Terminal
- npx expo start

This command starts the metro bundler. In the terminal window, we see the QR code followed by the Metro waiting on... and a manifest URL:

Let's notice the changes installing the expo-dev-client library:

  • The manifest URL contains expo-development-client along with the app scheme
  • The development server now operates for a development build (instead of Expo Go).

Since we do not have a development build installed on one of our devices or an emulator/simulator, we can't run our project yet.

2

Initialize a development build

Install EAS CLI

We need to install the EAS Command Line Interface (CLI) tool as a global dependency on our local machine. Run the following command:

Terminal
- npm install -g eas-cli

Log in or sign up for an Expo account

If you have an Expo account and are signed in using Expo CLI, skip this step. If you don't have an Expo account, sign up here and proceed with the login command described below.

To log in, run the following command:

Terminal
- eas login

This command asks for our Expo account email or username and password to complete the login.

Initialize and link the project to EAS

For any new project, the first step is to initialize and link it to the EAS servers. Run the following command:

Terminal
- eas init

On running, this command:

  • Requests verification of the account owner by entering our Expo account credentials and asks if we want to create a new EAS project:

    # Output after running eas init
✔ Which account should own this project? > your-username
✔ Would you like to create a project for @your-username/sticker-smash? … yes
✔ Created @your-username/sticker-smash
✔ Project successfully linked (ID: XXXX-XX-XX-XXXX) (modified app.json)

  • Creates EAS project and provides a link to that project which we can open in the Expo dashboard:

  • Generates a unique projectId and links this EAS project to the example app on our development machine.
  • Modifies app.json to include extra.eas.projectId and updates its value with the unique ID created.
What is projectId in app.json?

When eas init runs, it associates a unique identifier for our project in app.json under extra.eas.projectId. The value of this property is used to identify our project on EAS servers.

{
  "extra": {
    "eas": {
      "projectId": "0cd3da2d-xxx-xxx-xxx-xxxxxxxxxx"
    }
  }
}

3

Configure project for EAS Build

To set up our project for EAS Build, run the following command:

Terminal
- eas build:configure

On running, this command:

  • Prompts to select a platform: Android, iOS, or All. Since we are creating Android and iOS apps, let's select All.
  • Creates eas.json in the root of our project's directory with the following configuration:
eas.json
{
  "cli": {
    "version": ">= 8.0.0"
  },

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

    "preview": {
      "distribution": "internal"
    },

    "production": {}
  },

  "submit": {
    "production": {}
  }
}

This is the default configuration for eas.json in a new project. It does two things:

  • Defines the current EAS CLI version.
  • Adds three build profiles: development, preview, and production.
Explore development profile further

eas.json is a collection of different build profiles. Each profile is tailored with distinct configurations to produce specific build types. These profiles can also include platform-specific settings for Android or iOS.

Currently, our focus is on the development profile, which includes the following configuration:

  • developmentClient: Enabled (true) for creating a debug build. It loads the app using the expo-dev-client library, which provides development tools and generates a build artifact for device or emulator/simulator installation and allows using the app for local development as it supports updating the JavaScript on the fly.
  • distribution: Configured as internal to indicate that we want to share the build internally (instead of uploading it on app stores).

Note: Builds offer extensive customization options, including platform-specific settings and the ability to extend configurations across different build profiles. Learn more about customizing build profiles.

Summary

Chapter 1: Configure development build in cloud

We successfully used the EAS CLI to initialize, and configure our project, link it to EAS servers, and prepare a development build.

In the next chapter, let's create a development build for Android, install it on a device and an emulator, and get it running with the development server.

Next: Create and run a cloud build for Android