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我在将数据从 firestore 映射到模型时遇到问题。我已经尝试了几个小时，并且总是遇到诸如“地图无法转换为地图”或“类型'_InternalLinkedHashMap'不是'地图'类型的子类型之类的转换错误（异常）

我尝试了这些链接中的示例：

如何在 Flutter 中从 Cloud Firestore 加载数组和对象

https://github.com/dart-lang/sdk/issues/36836

还有更多，仍然不明白这东西是如何工作的。

这是我的实体和模型类：

实体

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:equatable/equatable.dart';

class ScreenHomeEntity extends Equatable {
  final String id;
  final String userName;
  final String userEmail;
  final String mainDoor;
  final Map<dynamic, dynamic> doors;

  const ScreenHomeEntity(
      this.id, this.userName, this.userEmail, this.mainDoor, this.doors);

  @override
  List<Object> get props => [id, userName, userEmail, mainDoor, doors];

  @override
  String toString() =>
      'ScreenHomeEntity {id: $id, userName: $userName, userEmail: $userEmail, mainDoor: $mainDoor, doors: $doors}';

  Map<String, Object> toJson() {
    return {
      'id': id,
      'userName': userName,
      'userEmail': userEmail,
      'mainDoor': mainDoor,
      'doors': doors,
    };
  }

  static ScreenHomeEntity fromJson(Map<String, Object> json) {
    return ScreenHomeEntity(
      json['id'] as String,
      json['userName'] as String,
      json['userEmail'] as String,
      json['mainDoor'] as String,
      json['doors'] as Map<dynamic, dynamic>,
    );
  }

  Map<String, Object> toDocument() {
    return {
      'userName': userName,
      'userEmail': userEmail,
      'mainDoor': mainDoor,
      'doors': doors,
    };
  }

  static ScreenHomeEntity fromDocument(DocumentSnapshot doc) {
    return ScreenHomeEntity(
      doc.documentID,
      doc.data['userName'],
      doc.data['userEmail'],
      doc.data['mainDoor'],
      doc.data['doors'],
    );
  }
}

模型：

import 'package:brava_flutter/data/entities/screen_home_entity.dart';
import 'package:meta/meta.dart';

@immutable
class ScreenHome {
  final String id;
  final String userName;
  final String userEmail;
  final String mainDoor;
  final Map<String, ScreenHomeDoor> doors;

  ScreenHome(this.userName,
      {String userEmail = '',
      String id,
      String mainDoor,
      Map<String, ScreenHomeDoor> doors})
      : this.userEmail = userEmail ?? '',
        this.id = id,
        this.mainDoor = mainDoor ?? '',
        this.doors = doors ?? Map<String, ScreenHomeDoor>();

  ScreenHome copyWith({
    String id,
    String userName,
    String userEmail,
    String mainDoor,
    Map<String, ScreenHomeDoor> doors,
  }) {
    return ScreenHome(
      userName ?? this.userName,
      id: id ?? this.id,
      userEmail: userEmail ?? this.userEmail,
      mainDoor: mainDoor ?? this.mainDoor,
      doors: doors ?? this.doors,
    );
  }

  @override
  int get hashCode =>
      id.hashCode ^
      userName.hashCode ^
      userEmail.hashCode ^
      mainDoor.hashCode ^
      doors.hashCode;

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is ScreenHome &&
          runtimeType == other.runtimeType &&
          id == other.id &&
          userName == other.userName &&
          userEmail == other.userEmail &&
          mainDoor == other.mainDoor &&
          doors == other.doors;

  @override
  String toString() =>
      'ScreenHomeModel {id: $id, userName: $userName, userEmail: $userEmail, mainDoor: $mainDoor, doors: $doors}';

  ScreenHomeEntity toEntity() =>
      ScreenHomeEntity(id, userName, userEmail, mainDoor, doors);

  static ScreenHome fromEntity(ScreenHomeEntity entity) {
    return ScreenHome(
      entity.userName,
      id: entity.id,
      userEmail: entity.userEmail,
      mainDoor: entity.mainDoor,
      doors: entity.doors, // EXCEPTION
    );
  }
}

class ScreenHomeDoor {
  String name;
  String address;

  ScreenHomeDoor.fromMap(Map<dynamic, dynamic> data)
      : name = data['name'],
        address = data['address'];
}

Firestore 数据示例： 在此处输入图像描述

4

1 回答 1

3

回答：

在模型中，方法“fromEntity”我没有将实体映射（动态）转换为模型映射（对象），而这正是发生异常的地方。这个动态地图中的每个“值”都应该被转换为对象，我一直都做错了。

  static ScreenHome fromEntity(ScreenHomeEntity entity) {
    return ScreenHome(
      entity.userName,
      id: entity.id,
      userEmail: entity.userEmail,
      mainDoor: entity.mainDoor,
      doors: entity.doors
          .map((k, v) => MapEntry(k as String, ScreenHomeDoor.fromMap(v))),
    );
  }

一直以来我都在尝试这样做MapEntry(k as String, v as ScreenHomeDoor.fromMap(v))

一个简单而愚蠢的错误......

于 2019-11-13T12:02:24.287 回答