Implement Rust’s Result Type in Dart (https://misha-krainik.medium.com/how-to-implement-rusts-result-type-in-dart-programming-language-df96ad3c7115)

typeResult.dart

enum Error {
  recordNotFound,
  notValidId,
}

class Result<T, E> {
  T? value;
  E? error;

  Result.Ok(T value) {
    this.value = value;
  }

  Result.Err(E error) {
    this.error = error;
  }

  dynamic then({required Function ok, required Function err}) {
    if (this.value != null) {
      return ok(value);
    }
    if (this.error != null) {
      return err(error);
    }
  }
}

class Record {
  int _id;

  get getId => _id;

  Record({required id}) : _id = id;

  String toString() => 'Record(id: $_id)';
}

class RecordStore {
  final _records;

  RecordStore({required records}) : _records = records;

  Result<Record, Error> getRecordById(int searchId) {
    if (searchId <= 0) return Result.Err(Error.notValidId);

    for (final record in _records) {
      if (record.getId == searchId) return Result.Ok(record);
    }
    return Result.Err(Error.recordNotFound);
  }
}



void main() {
  final store = RecordStore(
      records: List<Record>.generate(10, (genNum) => Record(id: genNum)));
  final result = store.getRecordById(-4);

  result.then(ok: (record) {
    print(record.toString());
  }, err: (error) {
    switch (error) {
      case Error.recordNotFound:
        print("Nothing to display at this time.");
        break;
      case Error.notValidId:
        print(
            "Invalid ID provided. Please enter a positive integer value for the record ID.");
    }
  });
}