Shared Preferences injection error using Stacked about flutter-tutorials

[harriseldon]

I did get it to not have errors with a few modifications.

1. within the app.dart, presolveUsing: LocalStorageServiceShared.getInstanceReady
   Notice that it is the actual function name. When the build_runner runs, it will covert it to the async function call
2. Null safety requires that you declare _instance as LocalStorageServiceShared?, but locator cannot resolve this to LocalStorageServiceShared. Therefore I changed your getInstanceReady function definition to not include the ? in type definition and changed the return to also do an explicit cast to LocalStorageServiceShared.

dependencies: [
  Presolve(
      classType: LocalStorageServiceShared,
      presolveUsing: LocalStorageServiceShared.getInstanceReady),
]

import 'package:shared_preferences/shared_preferences.dart';

class LocalStorageServiceShared {
  static LocalStorageServiceShared? _instance;
  static SharedPreferences? _preferences;
  
  // Changed from Future<LocalStorageServiceShared?> to Future<LocalStorageServiceShared>
  static Future<LocalStorageServiceShared> getInstanceReady() async {
    if (_instance == null) {
      _instance = LocalStorageServiceShared();
    }
    if (_preferences == null) {
      _preferences = await SharedPreferences.getInstance();
    }
    // Added explicit cast
    return (_instance as LocalStorageServiceShared);
  }
}

The resulting app.locator.dart now looks as follows

Future setupLocator() async {
  final localStorageServiceShared =
      await LocalStorageServiceShared.getInstanceReady();
  locator.registerSingleton(localStorageServiceShared);
}

Notice how the getInstanceReady was properly converted to the function getInstanceReady()

[JasmeetSingh30]

Awesome it worked. Thank you soooo much dude!!!!!! Now i know that i lack knowledge on null safety and OOP. Can you help me get a guide on these and anything more which will help me understand these basic concepts , i have just started with dart and flutter.