flutterdependency-inversionget-it

Is it possible to provide a null implementation when registering something on Flutter's GetIt?


Given we use third-party packages, one of them expects to receive a null in the production code and a custom implementation in the test code. So, it'll be convenient to have a GetIt provider that gives us null on production while an actual tailored implementation on tests.

We tried getIt.registerSingleton<OurOwnInterface?>(()=>null); but it doesn't even compile. And the documentation doesn't specify if that's possible or not.


Solution

  • One thing you could do is wrap it with a try catch:

    OurOwnInterface? _getOurOwnInterface() {
      try {
        return GetIt.I.get<OurOwnInterface>();
      } on StateError catch (_) {
        return null;
      }
    }
    

    The complete gist is here

    Edit:

    extension GetItExtension on GetIt {
      T? getOrNull<T extends Object>() {
        try {
          return GetIt.I.get<T>();
        } on StateError catch (_) {
          return null;
        }
      }
    }
    
    //and then use like:
    OurOwnInterface? appModel = GetIt.I.getOrNull();