The argument type 'Map<String, dynamic> Function()' can't be assigned to the parameter type 'Map<String, dynamic>'

Question

This could initially was working but after firebase update, it is now giving me this error. I have added asterisks to the part giving the error. The error message has been added beneath the code.

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;
}

The argument type 'Map<String, dynamic> Function()' can't be assigned to the parameter type 'Map<String, dynamic>'.

Answer 1

This works for me.

Record.fromSnapshot(DocumentSnapshot snapshot)
          : this.fromMap(snapshot.data() as Map<String, dynamic>, reference: snapshot.reference);

Answer 2

Try the following:

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

data() is a method:

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

that returns a Map<String, dynamic>

Answer 3

It's because DocumentSnapshot.data() is a function that returns Map<String, dynamic>.

So, the answer is:

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

Answer 4

Apparently all that was needed was parentheses on the maps

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>";
}