Question

这最初可以正常工作，但是在更新Firebase之后，现在却给了我这个错误。我在给出错误的部分添加了星号。错误消息已添加到代码下方。

import 'package:cloud_firestore/cloud_firestore.dart';

class Record {
  final String name;
  final int totalVotes;
  final DocumentReference reference;

  Record.fromMap(Map<String, dynamic> map, {this.reference})
      : assert(map['name'] != null),
        assert(map['totalVotes'] != null),
        name = map['name'],
        totalVotes = map['totalVotes'];

  Record.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(**snapshot.data**, reference: snapshot.reference);

  @override
  String toString() => "Record<$name:$totalVotes>";
}

class Voters {
  String uid;
  String voteId;
  String markedVoteOption;
}

参数类型'Map Function（）'不能分配给参数类型'Map '。

Answer 1

尝试以下操作：

  Record.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(snapshot.data(), reference: snapshot.reference);

data()是一种方法：

  /// Contains all the data of this [DocumentSnapshot].
  Map<String, dynamic> data() {
    return _CodecUtility.replaceDelegatesWithValueInMap(
        _delegate.data(), _firestore);
  }

返回一个Map<String, dynamic>

Answer 2

这是因为DocumentSnapshot.data()是一个返回Map<String, dynamic>的函数。

因此，答案是：

  Record.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(snapshot.data(), reference: snapshot.reference);

Answer 3

这就是我解决的方法。

import 'package:cloud_firestore/cloud_firestore.dart';

class Record {
  final String name;
  final int totalVotes;
  final DocumentReference reference;

  Record.fromMap(Map<String, dynamic> map(), {this.reference})
      : assert(map()['name'] != null),
        assert(map()['totalVotes'] != null),
        name = map()['name'],
        totalVotes = map()['totalVotes'];

  Record.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(snapshot.data, reference: snapshot.reference);

  @override
  String toString() => "Record<$name:$totalVotes>";
}

class Voters {
  String uid;
  String voteId;
  String markedVoteOption;
}


 /// Contains all the data of this [DocumentSnapshot].
  Map<String, dynamic> data() {
    return _CodecUtility.replaceDelegatesWithValueInMap(
        _delegate.data(), _firestore);
  }

Answer 4

显然，所有需要的只是地图上的括号

import 'package:cloud_firestore/cloud_firestore.dart';

class Record {
  final String name;
  final int votes;
  final DocumentReference reference;

  Record.fromMap(Map<String, dynamic> map(), {this.reference})
      : assert(map()['name'] != null),
        assert(map()['votes'] != null),
        name = map()['name'],
        votes = map()['votes'];

  Record.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(snapshot.data, reference: snapshot.reference);

  @override
  String toString() => "Record<$name:$votes>";
}

无法将参数类型'Map <String，dynamic> Function（）'分配给参数类型'Map <String，dynamic>'

4 个答案: