Config variables for React Native apps

Module to expose config variables to your javascript code in React Native, supporting both iOS and Android.

Bring some 12 factor love to your mobile apps!

Usage

Create a new file .env in the root of your React Native app:

API_URL=https://myapi.com
GOOGLE_MAPS_API_KEY=abcdefgh

Then access variables defined there from your app:

import Config from 'react-native-config'

Config.API_URL  // 'https://myapi.com'
Config.GOOGLE_MAPS_API_KEY  // 'abcdefgh'

Keep in mind this module doesn't obfuscate or encrypt secrets for packaging, so do not store sensitive keys in .env. It's basically impossible to prevent users from reverse engineering mobile app secrets, so design your app (and APIs) with that in mind.

Android

Config variables set in .env are available to your Java classes via BuildConfig:

public HttpURLConnection getApiClient() {
    URL url = new URL(BuildConfig.API_URL);
    // ...
}

You can also read them from your Gradle configuration:

defaultConfig {
    applicationId project.env.get("APP_ID")
}

And use them to configure libraries in AndroidManifest.xml and others:

<meta-data
  android:name="com.google.android.geo.API_KEY"
  android:value="@string/GOOGLE_MAPS_API_KEY" />

Once again keep in mind variables stored in .env are published with your code, so do not put anything sensitive there like your app signingConfigs.

iOS

Read variables declared in .env from your Obj-C classes like:

// import header
#import "ReactNativeConfig.h"

// then read individual keys like:
NSString *apiUrl = [ReactNativeConfig envFor:@"API_URL"];

// or just fetch the whole config
NSDictionary *config = [ReactNativeConfig env];

They're also available for configuration in Info.plist, by appending __RN_CONFIG_ to their name:

__RN_CONFIG_API_URL

Note: Requires specific setup (see below) and a Product > Clean is required after changing the values to see the updated values.

Different environments

Save config for different environments in different files: .env.staging, .env.production, etc.

By default react-native-config will read from .env, but you can change it when building or releasing your app.

Android

To pick which file to use in Android, set a variable in your build.gradle before the apply from: using all lowercase names:

project.ext.envConfigFiles = [
    debug: ".env.development",
    release: ".env.production",
    anycustombuildlowercase: ".env",
]

apply from: project(':react-native-config').projectDir.getPath() + "/dotenv.gradle"

Alternatively, you can set ENVFILE before building/running your app. For instance:

$ ENVFILE=.env.staging react-native run-android

iOS

Support for Xcode is still a bit experimental – but at this moment the recommendation is to create a new scheme for your app, and configure it to use a different env file.

To create a new scheme, open your app in Xcode and then:

• Click the current app scheme (button with your app name next to the stop button)
• Click "Manage Schemes..."
• Select your current scheme (the one on top)
• Click the settings gear below the list and select "Duplicate"
• Give it a proper name on the top left. For instance: "Myapp (staging)"

To make a scheme use a different env file, on the manage scheme window:

• Expand the "Build" settings on left
• Click "Pre-actions", and under the plus sign select "New Run Script Action"
• Fill in with this script on the dark box, replacing .env.staging for the file you want:

echo ".env.staging" > /tmp/envfile

This is still experimental and obviously a bit dirty – let me know if you have better ideas on this front!

Setup

Install the package:

$ npm install react-native-config --save

Link the library:

$ react-native link react-native-config

Extra step for iOS to support Info.plist

• Go to your project -> Build Settings -> All
• Search for "preprocess"
• Set Preprocess Info.plist File to Yes
• Set Info.plist Preprocessor Prefix File to ${CONFIGURATION_BUILD_DIR}/GeneratedInfoPlistDotEnv.h
• Set Info.plist Other Preprocessor Flags to -traditional
• If you don't see those settings, verify that "All" is selected at the top (instead of "Basic")

Extra step for Android

Apply a plugin to your app build in android/app/build.gradle:

// 2nd line, add a new apply:
apply from: project(':react-native-config').projectDir.getPath() + "/dotenv.gradle"

Advanced Android Setup

In android/app/build.gradle, if you use applicationIdSuffix or applicationId that is different from the package name indicated in AndroidManifest.xml in <manifest package="..."> tag, for example, to support different build variants: Add this in android/app/build.gradle

defaultConfig {
    ...
    resValue "string", "build_config_package", "YOUR_PACKAGE_NAME_IN_ANDROIDMANIFEST.XML"
}

Troubleshooting

Problems with Proguard

When Proguard is enabled (which it is by default for Android release builds), it can rename the BuildConfig Java class in the minification process and prevent React Native Config from referencing it. To avoid this, add an exception to android/app/proguard-rules.pro:

-keep class com.mypackage.BuildConfig { *; }

mypackage should match the package value in your app/src/main/AndroidManifest.xml file.