How to make inheritance hierarchy for Type Converter of Dart Floor?-CodePudding

As below, I define ListConverter<T> to make inheritance hierarchy.

abstract class ListConverter<T> extends TypeConverter<List<T>, String> {
  static const delimiter = "!DELIMITER!";

  T fromDB(String databaseValue);

  String toDB(T value);

  @override
  List<T> decode(String databaseValue) {
    return databaseValue
        .split(delimiter)
        .where((element) => element.isNotEmpty)
        .map((e) => fromDB(e))
        .toList();
  }

  @override
  String encode(List<T> value) {
    return value.map((e) => toDB(e)).join(delimiter);
  }
}

Using ListConverter<T>, I implement IntListConverter.

class IntListConverter extends ListConverter<int> {
  @override
  int fromDB(String databaseValue) {
    return int.parse(databaseValue);
  }

  @override
  String toDB(int value) {
    return value.toString();
  }
}

My plan was to use ListConverter<T> also on StringListConverter, etc. But unfortunately, I got this error message while running floor_generator.

[SEVERE] floor_generator:floor_generator on lib/persistence/db/app_database.dart: Only classes that inherit from TypeConverter can be used as type converters. Make sure use a class that inherits from TypeConverter.

I know that Hierarchy (B) works well, but I want to build (A) structure for managing other list converters.

(A) TypeConverter -> ListConverter -> IntListConverter
(B) TypeConverter -> IntListConverter

How to make inheritance hierarchy for Type Converter of Dart Floor?

CodePudding user response：

I resolved this problem in a roundabout way. I use mixin keyword instead of direct inheritance.

class IntListConverter extends TypeConverter<List<int>, String>
    with ListConverter<int> {
  @override
  int fromDB(String databaseValue) {
    return int.parse(databaseValue);
  }

  @override
  String toDB(int value) {
    return value.toString();
  }
}