Flutter/Dart: Subclass a freezed data class
Freezed doesn’t support inheritance at the moment so it’s recommended to use composition instead of inheritance as mentioned by the creator here:
https://github.com/rrousselGit/freezed/issues/464
And in the comments of the post.
Marco Papula
Updated on December 23, 2022Comments
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Marco Papula over 1 year
I am using the following plugin: https://pub.dev/packages/freezed
I want to subclass a freezed data class to provide additional functionality in my data layer. So I have my data class which looks like:
import 'dart:ui'; import 'package:freezed_annotation/freezed_annotation.dart'; part 'card.freezed.dart'; @freezed abstract class Card with _$Card { factory Card({String text, Color color, List<String> categories}) = _Card; }
Now I want to have this Card class as a super class to my CardModel so that the CardModel has access to the same fields, the copyWith method, value equality, ... But I have no Idea how to go about this. I am trying something like this:
import 'package:flutter/widgets.dart'; import 'package:growthdeck/features/card_deck/domain/entities/card.dart'; import '../../domain/entities/card.dart'; abstract class CardModel extends Card { factory CardModel.fromMap(Map<String, dynamic> card) => Card( text: card["text"], color: Color(int.parse(card['color'])), categories: card['categories'] as List<String>, ); }
Which throws the following error:
package:growthdeck/features/card_deck/data/models/card_model.dart 11:9 new CardModel.fromMap test/features/card_deck/data/models/card_model_test.dart 13:23 main.<fn> type '_$_Card' is not a subtype of type 'CardModel' in type cast
Is there any way to do this properly? My workaround would be to simply "wrap" the Card class inside the CardModel and provide a toCard() method which is not very elegant :S