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

Declare config variables in .env:

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

Then access from your app:

import Config from 'react-native-config'

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

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:

signingConfigs {
    release {
        storeFile file(project.env.get("RELEASE_STORE_FILE"))
        storePassword project.env.get("RELEASE_STORE_PASSWORD")
        keyAlias project.env.get("RELEASE_KEY_ALIAS")
        keyPassword project.env.get("RELEASE_KEY_PASSWORD")
    }
}

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" />

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];

Support for plist files is missing. We'd love to be able to refer to config from .env there, but haven't found a way to support this yet. Let us know if you have ideas!

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.config before the apply from::

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