_InternalLinkedHashMap<String, dynamic> 不是“Map<String, String>”类型的子类型

Question

使用下面显示的代码，我在此行收到错误（此行位于以下完整代码 sn-p 的底部）：

address: data['address'] ??

我可以理解这可能意味着什么或导致什么。有人有想法吗？

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:equatable/equatable.dart';
import 'package:keekz_mvp/config/paths.dart';
import 'package:meta/meta.dart';
import 'package:keekz_mvp/models/models.dart';

class Keekz extends Equatable {
  final String id;
  final User author;
  final String imageUrl;
  final String caption;
  final int likes;
  final DateTime date;
  final GeoPoint location;
  final Map<String, String> address;

  const Keekz({
    this.id,
    @required this.author,
    @required this.imageUrl,
    @required this.caption,
    @required this.likes,
    @required this.date,
    @required this.location,
    @required this.address,
  });

  @override
  List<Object> get props => [
        id,
        author,
        imageUrl,
        caption,
        likes,
        date,
        location,
        address,
      ];

  Keekz copyWith({
    String id,
    User author,
    String imageUrl,
    String caption,
    int likes,
    DateTime date,
    GeoPoint location,
    Map<String, String> address,
  }) {
    return Keekz(
      id: id ?? this.id,
      author: author ?? this.author,
      imageUrl: imageUrl ?? this.imageUrl,
      caption: caption ?? this.caption,
      likes: likes ?? this.likes,
      date: date ?? this.date,
      location: location ?? this.location,
      address: address ?? this.address,
    );
  }

  Map<String, dynamic> toDocument() {
    return {
      'author':
          FirebaseFirestore.instance.collection(Paths.users).doc(author.id),
      'imageUrl': imageUrl,
      'caption': caption,
      'likes': likes,
      'date': Timestamp.fromDate(date),
      'location': location,
      'address': address,
    };
  }

  static Future<Keekz> fromDocument(DocumentSnapshot doc) async {
    if (doc == null) return null;
    final data = doc.data();
    final authorRef = data['author'] as DocumentReference;
    if (authorRef != null) {
      final authorDoc = await authorRef.get();
      if (authorDoc.exists) {
        return Keekz(
          id: doc.id,
          author: User.fromDocument(authorDoc),
          imageUrl: data['imageUrl'] ?? '',
          caption: data['caption'] ?? '',
          likes: (data['likes'] ?? 0).toInt(),
          date: (data['date'] as Timestamp)?.toDate(),
          location: data['location'] ?? GeoPoint(0, 0),
          address: data['address'] ??
              {
                'city': 'not set',
                'postalcode': 'not set',
                'country': 'not set'
              },
        );
      }
    }
    return null;
  }
}

Answer 1

你可以试试这个吗？

address: data['address']!=null ? jsonDecode(data['address']) :

我认为数据来自转换为字符串的firebase，..所以它需要在将其用作 Map

之前进行 jsondecode

Answer 2

此错误意味着地址需要 类型的映射，但它正在接收 类型的映射

因此，请在代码的第 9 行进行更改：

final Map<String, String> address;

进入这个：

final Map<String, dynamic> address;

这意味着您的data['address'] 没有返回null，否则它会被分配not set 的默认字符串值，但实际上data['address'] 正在返回_InternalLinkedHashMap<String, dynamic> 类型的映射。

应该可以解决你的问题。

Answer 3

发生此错误是因为 Map 正在等待，并且您在 Address 中定义了 Map 。

必须替换地址变量中的数据类型，应该如下：

Map <String, dynamic> address;