Setting environment variables in Flutter

Question

For example, building a client for an API, like Twitch.

In a Dart CLI binary, I could use a generic environment variable, or a Dart definition variable. For example,

Answer 1

Since I was trying to solve this as well and encountered this thread I just wanted to add this for people looking for a solution in the future... If all you're looking for is PROD/DEV environments there is now a supported way of getting if the app is in production or not:

const bool isProduction = bool.fromEnvironment('dart.vm.product');

As suggested by:

https://twitter.com/FlutterDev/status/1048278525432791041

https://github.com/flutter/flutter/issues/4014

Answer 2

Create a class:

import 'package:flutter/foundation.dart';

class AppUtils {
  static String get clientId {
    if (kDebugMode) return 'debug_id';
    else if (kProfileMode) return 'profile_id';
    else if (kReleaseMode) return 'production_id';
    else if (kIsWeb) return 'web_mode_id';
    
    throw ArgumentError('No mode detected');
  }
}

Usage:

var id = AppUtils.clientId;

Answer 3

Starting from Flutter 1.17 you can define compile-time variables if you want to.

To do so just use --dart-define argument during flutter run or flutter build

If you need to pass multiple key-value pairs, just define --dart-define multiple times:

flutter run --dart-define=SOME_VAR=SOME_VALUE --dart-define=OTHER_VAR=OTHER_VALUE

and then, anywhere in your code you can use them like:

const SOME_VAR = String.fromEnvironment('SOME_VAR', defaultValue: 'SOME_DEFAULT_VALUE');
const OTHER_VAR = String.fromEnvironment('OTHER_VAR' defaultValue: 'OTHER_DEFAULT_VALUE');

Also, they can be used in native layers too.

If something - here is an article that explains more

Answer 4

For configuration a common pattern I've seen is to use separate main files instead. i.e.

flutter run -t lib/production_main.dart

and

flutter build apk -t lib/debug_main.dart

And then in those different main files set up the configurations desired.

In terms of reading ids, you can do that from arbitrary assets https://flutter.io/assets-and-images/.

I believe it is possible in Flutter to read from the environment as you suggest, however I don't know how to set those environment variables on iOS or Android.