Question

我有以下要加载到Flutter应用程序中的JSON数据：

{
    "Games": [
        {
            "name": "Sample Name",
            "categories": [
                {
                    "name": "Category 1",
                    "multiplier": 1,
                    "order": 2
                },
                {
                    "name": "Category 2",
                    "order": 9,
                    "Range": [
                        {
                            "ceiling": 0,
                            "floor": 0,
                            "score": 0
                        },
                        {
                            "ceiling": 1,
                            "floor": 1,
                            "score": 2
                        }
                    ]
                },
                {
                    "name": "Category 4",
                    "multiplier": -1,
                    "order": 11,
                    "penalty": true
                },
                {
                    "name": "Category 5",
                    "multiplier": 1,
                    "order": 8
                },
                {
                    "name": "Category 6",
                    "multiplier": -1,
                    "order": 10,
                    "penalty": true
                }
            ],
            "enabled": true,
            "maxPlayers": 4,
            "minPlayers": 1
        }
    ]
}

我正在使用以下代码从上面的地图填充对象：

class Entry {
  String name;
  // final String filename;
  int minPlayers;
  int maxPlayers;
  bool enabled;
  bool selected = false;
  DocumentReference reference;
  List<Category> categories;

  Entry.fromMap(Map<String, dynamic> map, {this.reference}) {
    name = map['name'];
    enabled = map['enabled'];
    minPlayers = map['minPlayers'];
    maxPlayers = map['maxPlayers'];

    categories =
        (map['categories'].map((data) => Category.fromMap(data)).toList());
  }

class Category {
  String name;
  int order;
  int multiplier;
  bool penalty;

  Category.fromMap(Map<String, dynamic> map, {DocumentReference reference}) {
    name = map['name'];
    order = map['order'];
    multiplier = map['multiplier'];
    penalty = !map.containsKey('penalty');
  }

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

运行它时，出现以下错误：

type '_InternalLinkedHashMap<dynamic, dynamic>' is not a subtype of type 'Map<String, dynamic>'

如何将类别元素的集合放入可迭代的对象列表中，以容纳每个类别，然后从map ['categories']中的单个元素加载该类别？

Answer 1

我稍微重构了您的代码，但由于我无权访问其代码，因此删除了该引用。我试过了，效果很好

class Entry{
  String name;
  // final String filename;
  int minPlayers;
  int maxPlayers;
  bool enabled;
  bool selected;
  List<Category> categories;
  Entry({
    this.name,
    this.minPlayers,
    this.maxPlayers,
    this.enabled,
    this.categories,
    this.selected =false
  });

  factory Entry.fromMap(Map<String, dynamic> map) {
    return Entry(
      name: map['name'],
      enabled: map['enabled'],
      minPlayers: map['minPlayers'],
      maxPlayers: map['maxPlayers'],
      categories: Category.fromList(map['categories'])
    );
  }
  static List<Entry> fromList(List json) {
    return json.map((entry) => Entry.fromMap(entry)).toList();
  }
}

class Category {
  String name;
  int order;
  int multiplier;
  bool penalty;
  Category(
    {
      this.name,
      this.order,
      this.multiplier,
      this.penalty
    }
  );

  factory Category.fromMap(Map<String, dynamic> map) {

    return Category(
      name :map['name'],
      order : map['order'],
      multiplier : map['multiplier'],
      penalty : map['penalty'] ?? false  
    );
  }

  static List<Category> fromList(List json) {
    return json.map((category) => Category.fromMap(category)).toList();
  }

}

并解码您提供的示例，请使用：

List<Entry> entries = Entry.fromList(test["Games"]);

Answer 2

我认为您尚未为各自的json创建有效的dart类。您的json具有类似Entry类的体系结构，其中包含多个游戏，

每个游戏都有多个类别，

每个类别具有多个范围。

请使用this工具将json转换为Dart类

我已经为您的json创建了模型类，请检查this链接。

现在该解析了。我只是将欢迎班改名为Entry。

解析

 final jsonResponse = json.decode('YOUR JSON STRING');
Entry entry =Entry.fromJson(jsonResponse);
print(entry.games.length);
entry.games.map((game) {
  print("Game Name " + game.name + "----------");
  print("Category List");
  game.categories.map((category) {
    print(category.name);

  }).toList();
}).toList();

现在检查调试控制台。所有类别和游戏显示。

将地图项目阅读为班级成员

2 个答案: