What's the best practice to keep all the constants in Flutter?

Question

What\'s the best programming practice to

create a constant class in Flutter

to keep all the application constants for easy referenc

Answer 1

EDIT

Now that the flag --dart-define has been added to the different command lines of Flutter, the following answer no-longer applies.

Instead just declare constants wherever you want, and potentially refer to other answers.

---

While there are no technical issues with static const, architecturally you may want to do it differently.

Flutter tend to not have any global/static variables and use an InheritedWidget.

Which means you can write:

class MyConstants extends InheritedWidget {
  static MyConstants of(BuildContext context) => context. dependOnInheritedWidgetOfExactType();

  const MyConstants({Widget child, Key key}): super(key: key, child: child);

  final String successMessage = 'Some message';

  @override
  bool updateShouldNotify(MyConstants oldWidget) => false;
}

Then inserted at the root of your app:

void main() {
  runApp(
    MyConstants(
      child: MyApp(),
    ),
  );
}

And used as such:

@override
Widget build(BuilContext context) {
  return Text(MyConstants.of(context).successMessage);
}

---

This has a bit more code than the static const, but offer many advantages:

• Works with hot-reload
• Easily testable and mockable
• Can be replaced with something more dynamic than constants without rewriting the whole app.

But at the same time it:

1. Doesn't consume much more memory (the inherited widget is typically created once)
2. Is performant (Obtaining an InheritedWidget is O(1))