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iOS build process

This page describes the process of building iOS projects with EAS Build. You may want to read this if you are interested in the implementation details of the build service.

Build Process

Let's take a closer look at the steps for building iOS projects with EAS Build. We'll first run some steps on your local machine to prepare the project and then we'll actually build the project on a remote service.

The first phase happens on your computer. EAS CLI is in charge of completing the following steps:
  1. Check if the git index is clean - this means if there aren't any uncommitted changes. If it's not clean an error is thrown.
  2. Prepare the credentials needed for the build.
    • Depending on the value of builds.ios.PROFILE_NAME.credentialsSource, the credentials are obtained from either the local credentials.json file or from the EAS servers. If the auto or remote mode is selected but no credentials exist yet, you're offered to generate them.
  3. Generic projects require an additional step: check whether the Xcode project is configured to be buildable on the EAS servers (i.e. ensure the correct bundle identifier and Apple Team ID are set).
  4. Create the tarball containing shallow clone of your local repository (git clone --depth 1 ...).
  5. Upload the project tarball to a private AWS S3 bucket and send the build request to EAS Build.

In this next phase, this is what happens when EAS Build picks up your request:
  1. Create a new macOS VM for the build.
    • Every build gets its own fresh macOS VM with all build tools installed there (Xcode, Fastlane, and so on).
  2. Download the project tarball from a private AWS S3 bucket and unpack it.
  3. Run yarn install in the project root (or npm install if yarn.lock does not exist).
  4. Managed projects require an additional step: Run expo prebuild to convert the project to a generic one.
  5. Run pod install in the ios directory inside your project.
  6. Restore the credentials:
    • Create a new keychain.
    • Import the Distribution Certificate into the keychain.
    • Write the Provisioning Profile to the ~/Library/MobileDevice/Provisioning Profiles directory.
    • Verify that the Distribution Certificate and Provisioning Profile match (every Provisioning Profile is assigned to a particular Distribution Certificate and cannot be used for building the iOS with any other certificate).
    • Update the Xcode project with the ID of the Provisioning Profile.
  7. Create Gymfile in the ios directory if it does not already exist (check out the Default Gymfile section).
  8. Run fastlane gym in the ios directory.
  9. Upload the build artifact to a private AWS S3 bucket.
    • The artifact path can be configured in eas.json at builds.ios.PROFILE_NAME.artifactPath. It defaults to ios/build/App.ipa. You can specify a glob-like pattern for artifactPath. We're using the fast-glob package under the hood.

We're using Fastlane for building iOS projects. To be more precise, we're using the fastlane gym command (see the Fastlane docs to learn more). This command allows you to declare the build configuration in Gymfile.
EAS Build can use your own Gymfile. All you need to do is to place this file in the ios directory.

If the ios/Gymfile file doesn't exist, the iOS builder creates a default one. It looks something like this:
suppress_xcode_output(true)
clean(true)

scheme("app")

export_options({
  method: "app-store",
  provisioningProfiles: {
    "com.expo.eas.builds.test.application" => "dd83ed9c-4f89-462e-b901-60ae7fe6d737"
  }
})

export_xcargs "OTHER_CODE_SIGN_FLAGS=\"--keychain /tmp/path/to/keychain\""

disable_xcpretty(true)

output_directory("./build")
output_name("App")