如何从 JSON 响应 DART 返回前五个值

Question

我想从上面的 JSON 响应中返回 name 的前五个值

Future <List<UserModel>> fetchData() async {
  final response =
      await http.get(Uri.parse(URLCONST.API_URL));
  if (response.statusCode == 200) {
    List jsonResponse = json.decode(response.body);
    return jsonResponse.map((user) => new UserModel.fromJson(user)).toList();
    
  } else {
    throw Exception('Unexpected error occured!');
  }
}

这是下面的模型。

class UserModel {
  int id;
  String name;

  UserModel({
    required this.id,
    required this.name,

  });

  factory UserModel.fromJson(Map<String, dynamic> json) {
    return UserModel(
      id: json['id'],
      name: json['name'],

    );
  }
}

API 在列表中有几个值，我想只返回前 5 个

Answer 1

如果我理解正确，你可以这样做：

jsonResponse.map((user) => new UserModel 
                .fromJson(user))
                // this will take only the first five elements of the iterable
                .take(5)
                // this will map each user to its corresponding name
                .map((user) => user.name)
                // this, as you already know, will convert the iterable to a list
                .toList();

这将返回一个包含前五个名称的List<String>