Question 270391 in Flutter Question posted in
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why a named constructor in a class with final propertieses most has all the final properties in flutter?

enter image description here

In this class I dont want to (chatCard.person) named constructor has subtitle property.Because I dont need it.But as you can see I have this error :All final variables must be initialized, but ‘subtitle’ isn’t.
Try adding an initializer for the field.
I know that If I remove final keyWord from its definition in third line the error will remove But then the class isnt immutable.
So any idea?

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2

Answers


  1. 0

    You can use a factory constructor that doesn’t include the subtitle property:

    class ChatCard extends StatelessWidget {
  const ChatCard._({
    this.title,
    this.subtitle,
    this.lastSeenTime,
    this.lastMessageTime,
    this.pic,
    this.unSeenMessageNumber,
    this.memberSubscribeNumber,
    this.isOnline,
    this.seenStatus,
  });

  factory ChatCard.person({
    required String? title,
    required String? lastSeenTime,
    required String? lastMessageTime,
    required String? pic,
    required String? unSeenMessageNumber,
    required String? memberSubscribeNumber,
    required bool? isOnline,
    required bool? seenStatus,
  }) =>
      ChatCard._(
        title: title,
        lastSeenTime: lastSeenTime,
        lastMessageTime: lastMessageTime,
        pic: pic,
        unSeenMessageNumber: unSeenMessageNumber,
        memberSubscribeNumber: memberSubscribeNumber,
        isOnline: isOnline,
        seenStatus: seenStatus,
      );

  final String? title;
  final String? subtitle;
  final String? lastSeenTime;
  final String? lastMessageTime;
  final String? pic;
  final String? unSeenMessageNumber;
  final String? memberSubscribeNumber;
  final bool? isOnline;
  final bool? seenStatus;

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    throw UnimplementedError();
  }
}
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  2. 0

    You can follow like

      const ChatCard.person({
    super.key,
     .....
  }) : subtitle = null;
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