Expo-modules-core NPM

The core of Expo Modules architecture.

Installation in managed Expo projects

For managed Expo projects, please follow the installation instructions in the API documentation for the latest stable release. If you follow the link and there is no documentation available then this library is not yet usable within managed projects — it is likely to be included in an upcoming Expo SDK release.

Installation in bare React Native projects

For bare React Native projects, you must ensure that you have installed and configured the expo package before continuing.

Add the package to your npm dependencies

npm install expo-modules-core

Configure for iOS

Run npx pod-install after installing the npm package.

Configure for Android

No additional set up necessary.

Importing native dependencies - autolinking

Many React Native libraries come with platform-specific (native) code. This native code has to be linked into the project and, in some cases, configured further. These actions require some modifications to the native project files. One of the steps that has to be done with the native configuration is to enable the autolinking mechanism that takes care of including any supported module's native code into the project. The following configuration is required:

iOS

Caution! After you have made the following changes you will need to run pod install again.

# Podfile

require File.join(File.dirname(`node --print "require.resolve('react-native/package.json')"`), "scripts/react_native_pods")
require File.join(File.dirname(`node --print "require.resolve('expo-modules-core/package.json')"`), "cocoapods.rb")
require File.join(File.dirname(`node --print "require.resolve('expo-modules-core/package.json')"`), "scripts/autolinking")

#  ...

target "TargetName" do
  use_unimodules!
  config = use_native_modules!
  use_react_native!(:path => config["reactNativePath"])

  # ...
end

Android

// app/build.gradle

apply from: new File(["node", "--print", "require.resolve('expo-modules-core/package.json')"].execute(null, rootDir).text.trim(), "../gradle.groovy")
apply from: new File(["node", "--print", "require.resolve('react-native/package.json')"].execute(null, rootDir).text.trim(), "../react.gradle")
apply from: new File(["node", "--print", "require.resolve('expo-updates/package.json')"].execute(null, rootDir).text.trim(), "../scripts/create-manifest-android.gradle")

// ...

apply from: new File(["node", "--print", "require.resolve('@react-native-community/cli-platform-android/package.json')"].execute(null, rootDir).text.trim(), "../native_modules.gradle");
applyNativeModulesAppBuildGradle(project)

// settings.gradle

apply from: new File(["node", "--print", "require.resolve('expo-modules-core/package.json')"].execute(null, rootDir).text.trim(), "../gradle.groovy");
includeUnimodulesProjects()

apply from: new File(["node", "--print", "require.resolve('@react-native-community/cli-platform-android/package.json')"].execute(null, rootDir).text.trim(), "../native_modules.gradle");
applyNativeModulesSettingsGradle(settings)

Explanation

The scripts that are referenced in Gradle and Cocoapods are usually found the related package inside the project's node_modules directory. In the case of monorepos (such as Yarn workspaces) the project directory may not contain node_modules at all; instead, the modules are likely to be located at the root of the repository. In order to ensure that both cases are supported, we take advantage of the Node dependency resolution strategy. We invoke a subprocess that spawns the simple JavaScript snippet that tries to locate the desired npm package containing the script we need.

On iOS, we use ` ` (backtick) (alternative reference).
On Android, we use String[]#execute to obtain the results from the subprocess' stdout.

The Node process that is spawned runs require.resolve to obtain the path to a module's package.json(if you look for the module location using solely module name, you'll be given the path to the file pointed by the main attribute from the package.json and we need to know the location of the module's root directory). We then assemble the path to the desired script and execute it.