如何从postman api的数据集合的嵌套列表中获取数据集合到dart Flutter中的列表<dynamic>

Question

我有一个邮递员 API 调用。但我不知道如何在邮递员 API 的 API 调用中从应用程序 JSON 值中提取数据。有人可以向我解释一下如何在 dart 数据模型中提取它吗？

{
"deviceType": "andriod",
"deviceId": "C6179909526098",
"deviceName": "Samsung-MT200",
"deviceOSVersion": "2.3.6",
"deviceIPAddress": "11.433.445.66",
"lat": 9.9312,
"long": 76.2673,
"buyer_gcmid": "",
"buyer_pemid": "",
"app": {
    "version": "1.20.5",
    "installTimeStamp": "2022-02-10T12:33:30.696Z",
    "uninstallTimeStamp": "2022-02-10T12:33:30.696Z",
    "downloadTimeStamp": "2022-02-10T12:33:30.696Z"
}

}

这是数据模型。

    class SplashPost {
  String? deviceType;
  String? deviceId;
  String? deviceName;
  String? deviceOSVerion;
  String? deviceIPAddress;
  String? lat;
  String? long;
  String? buyer_gcmid;
  String? buyer_pemid;
  String? version;
  List<dynamic>? app;

  SplashPost({
    required this.deviceType,
    required this.deviceIPAddress,
    required this.deviceId,
    required this.deviceName,
    required this.deviceOSVerion,
    required this.app,
    required this.buyer_gcmid,
    required this.buyer_pemid,
    required this.lat,
    required this.long,
    required this.version,
  });

  factory SplashPost.fromJson(Map<String, dynamic> json) => SplashPost(
        deviceIPAddress: json["deviceIPAddress"],
        deviceType: json["deviceType"],
        deviceId: json["deviceId"],
        deviceName: json["deviceName"],
        deviceOSVerion: json["deviceOSVersion"],
        lat: json["lat"],
        long: json["long"],
        version: json["version"],
        buyer_gcmid: json["buyer_gcmid"],
        buyer_pemid: json["buyer_pemid"],
        app: List<dynamic>.from(json["app"]).map((x) => x),
      );
}

Map<String, dynamic> toJson() => {
      "version": version,
      "installTimeStamp": installTimeStamp,
      "uninstallTimeStamp": uninstallTimeStamp,
      "downloadTimeStamp": downloadTimeStamp,
    };

这是数据模型文件，我不知道如何从“app”JSON 值中提取数据。 它让我犯了

的错误

参数类型“Iterable”无法分配给参数类型“List”？在应用程序价值列表中。

和

未定义名称“版本”

有人可以解释并解决我的问题吗。

Answer 1

我个人喜欢使用网站 https://app.quicktype.io/ 从响应生成一个类。它有一些设置可以根据您的喜好进行调整，如果设置不能涵盖它，您当然可以手动进行调整。这是该网站的示例输出，使用您的回复。

import 'dart:convert';

class SplashPost {
    String deviceType;
    String deviceId;
    String deviceName;
    String deviceOsVersion;
    String deviceIpAddress;
    double lat;
    double long;
    String buyerGcmid;
    String buyerPemid;
    App app;

    SplashPost({
        required this.deviceType,
        required this.deviceId,
        required this.deviceName,
        required this.deviceOsVersion,
        required this.deviceIpAddress,
        required this.lat,
        required this.long,
        required this.buyerGcmid,
        required this.buyerPemid,
        required this.app,
    });

    factory SplashPost.fromJson(String str) => SplashPost.fromMap(json.decode(str));

    String toJson() => json.encode(toMap());

    factory SplashPost.fromMap(Map<String, dynamic> json) => SplashPost(
        deviceType: json["deviceType"],
        deviceId: json["deviceId"],
        deviceName: json["deviceName"],
        deviceOsVersion: json["deviceOSVersion"],
        deviceIpAddress: json["deviceIPAddress"],
        lat: json["lat"]?.toDouble(),
        long: json["long"]?.toDouble(),
        buyerGcmid: json["buyer_gcmid"],
        buyerPemid: json["buyer_pemid"],
        app: App.fromMap(json["app"]),
    );

    Map<String, dynamic> toMap() => {
        "deviceType": deviceType,
        "deviceId": deviceId,
        "deviceName": deviceName,
        "deviceOSVersion": deviceOsVersion,
        "deviceIPAddress": deviceIpAddress,
        "lat": lat,
        "long": long,
        "buyer_gcmid": buyerGcmid,
        "buyer_pemid": buyerPemid,
        "app": app.toMap(),
    };
}

class App {
    String version;
    DateTime installTimeStamp;
    DateTime uninstallTimeStamp;
    DateTime downloadTimeStamp;

    App({
        required this.version,
        required this.installTimeStamp,
        required this.uninstallTimeStamp,
        required this.downloadTimeStamp,
    });

    factory App.fromJson(String str) => App.fromMap(json.decode(str));

    String toJson() => json.encode(toMap());

    factory App.fromMap(Map<String, dynamic> json) => App(
        version: json["version"],
        installTimeStamp: DateTime.parse(json["installTimeStamp"]),
        uninstallTimeStamp: DateTime.parse(json["uninstallTimeStamp"]),
        downloadTimeStamp: DateTime.parse(json["downloadTimeStamp"]),
    );

    Map<String, dynamic> toMap() => {
        "version": version,
        "installTimeStamp": installTimeStamp.toIso8601String(),
        "uninstallTimeStamp": uninstallTimeStamp.toIso8601String(),
        "downloadTimeStamp": downloadTimeStamp.toIso8601String(),
    };
}

Answer 2

您的

json["app"]

属于

Map<String, dynamic> json

类型，这就是为什么

List<dynamic>.from(json["app"])

不起作用。

您需要将

app

的类型更改为：

Map<String, dynamic> app;

并像这样解析它

factory SplashPost.fromJson(Map<String, dynamic> json) => SplashPost(
  // ... rest of code
  app: json['app'] ?? {}
)

或者您可以创建一个新课程

SplashPostApp

并实施

factory SplashPostApp.fromJson(Map<String, dynamic> json) ...

然后在您的

SplashPost

类中将

app

的类型更改为

SplashPostApp

并将其解析为：

factory SplashPost.fromJson(Map<String, dynamic> json) => SplashPost(
...
app: SplashPostApp.fromJson(json['app']?? {})