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, using both as fallbacks:

main() {   String clientId =        // dart -dCLIENT_ID='abc bin/example.dart       // This is considered "compiled-into" the application.       const String.fromEnvironment('CLIENT_ID') ??        // CLIENT_ID='abc' dart bin/example.dart       // This is considered a runtime flag.       Platform.environment['CLIENT_ID'];    // Use clientId. } 

Does Flutter have a way of setting either/both of these, specifically...

• During dev time
• When shipped to prod

Happy to help with some docs once I figure out how :)

Answer 1

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.

Answer 2

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.

Here is an article that explains more.