Question

我正在尝试将两个Built_value类组合到一个HTTP POST请求中。我的功能如下：

Future<void> changeInfo(BasicInfo basicInfo, Notifications notifications) async {
  String json = jsonEncode({
    'basicInfo': basicInfo.toJson(),
    'notifications': notifications.toJson()
  });
  print(json) // This is double encoding my basicInfo and notifications classes
  // resulting in something like this with forward slashes \:
  // {"basicInfo":"{\"gender\":"Male"}","notifications":"{\"emailOnMessage\":true}"}
  final response = await http.post(myUrl, body: json, headers: {
    'Content-type': 'application/json'
  });
  // etc
}

但是，由于外部jsonEncode和内部toJson（），我相信basicInfo和通知已被双重编码。如果删除toJson（）方法，则使用奇怪的正斜杠会得到相同的结果。

当我将其写入数据库时，我在数据库中得到的字符串类似于

"{\"gender\":"Male"}"

和

{\"emailOnMessage\":true}"}

任何帮助将不胜感激。谢谢

Answer 1

请使用以下代码段和类来获取正确的json字符串
代码段

  Payload payload = Payload(basicInfo: BasicInfo(gender: "male"),notifications: Notifications(emailOnMessage: true));
  String jsonString = payloadToJson(payload);
  print('${jsonString}');

输出，您可以看到图片

I/flutter (22155): {"basicInfo":{"gender":"male"},"notifications":{"emailOnMessage":true}}

要解析和组装的相关类

// To parse this JSON data, do
//
//     final payload = payloadFromJson(jsonString);

import 'dart:convert';

Payload payloadFromJson(String str) => Payload.fromJson(json.decode(str));

String payloadToJson(Payload data) => json.encode(data.toJson());

class Payload {
    BasicInfo basicInfo;
    Notifications notifications;

    Payload({
        this.basicInfo,
        this.notifications,
    });

    factory Payload.fromJson(Map<String, dynamic> json) => Payload(
        basicInfo: BasicInfo.fromJson(json["basicInfo"]),
        notifications: Notifications.fromJson(json["notifications"]),
    );

    Map<String, dynamic> toJson() => {
        "basicInfo": basicInfo.toJson(),
        "notifications": notifications.toJson(),
    };
}

class BasicInfo {
    String gender;

    BasicInfo({
        this.gender,
    });

    factory BasicInfo.fromJson(Map<String, dynamic> json) => BasicInfo(
        gender: json["gender"],
    );

    Map<String, dynamic> toJson() => {
        "gender": gender,
    };
}

class Notifications {
    bool emailOnMessage;

    Notifications({
        this.emailOnMessage,
    });

    factory Notifications.fromJson(Map<String, dynamic> json) => Notifications(
        emailOnMessage: json["emailOnMessage"],
    );

    Map<String, dynamic> toJson() => {
        "emailOnMessage": emailOnMessage,
    };
}

完整代码

import 'package:flutter/material.dart';
import 'dart:convert';

// To parse this JSON data, do
//
//     final payload = payloadFromJson(jsonString);

Payload payloadFromJson(String str) => Payload.fromJson(json.decode(str));

String payloadToJson(Payload data) => json.encode(data.toJson());

class Payload {
  BasicInfo basicInfo;
  Notifications notifications;

  Payload({
    this.basicInfo,
    this.notifications,
  });

  factory Payload.fromJson(Map<String, dynamic> json) => Payload(
    basicInfo: BasicInfo.fromJson(json["basicInfo"]),
    notifications: Notifications.fromJson(json["notifications"]),
  );

  Map<String, dynamic> toJson() => {
    "basicInfo": basicInfo.toJson(),
    "notifications": notifications.toJson(),
  };
}

class BasicInfo {
  String gender;

  BasicInfo({
    this.gender,
  });

  factory BasicInfo.fromJson(Map<String, dynamic> json) => BasicInfo(
    gender: json["gender"],
  );

  Map<String, dynamic> toJson() => {
    "gender": gender,
  };
}

class Notifications {
  bool emailOnMessage;

  Notifications({
    this.emailOnMessage,
  });

  factory Notifications.fromJson(Map<String, dynamic> json) => Notifications(
    emailOnMessage: json["emailOnMessage"],
  );

  Map<String, dynamic> toJson() => {
    "emailOnMessage": emailOnMessage,
  };
}


void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      Payload payload = Payload(basicInfo: BasicInfo(gender: "male"),notifications: Notifications(emailOnMessage: true));
      String jsonString = payloadToJson(payload);
      print('${jsonString}');

      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

将多个toJson方法合并为一个请求

1 个答案: