检查 Json 响应颤动中是否存在值答案

【问题标题】：check if value exists inside Json response flutter检查 Json 响应颤动中是否存在值
【发布时间】：2020-02-22 05:08:23
【问题描述】：

我提出了一个Json 发布请求并得到如下回复：

[{id: 13, mentor_id: 5, mentee_id: 184, status: null, session_count: 0, current_job: null, email: null, phone_call: null, video_call: null, face_to_face: null, created_at: 2020-02-20 20:37:50, updated_at: 2020-02-20 20:37:50}, {id: 14, mentor_id: 8, mentee_id: 184, status: null, session_count: 0, current_job: null, email: null, phone_call: null, video_call: null, face_to_face: null, created_at: 2020-02-21 22:39:31, updated_at: 2020-02-21 22:39:31}]

现在，我想检查id 键是否等于某个数字，以便设置按钮的状态。例如：

if(id contains 5){
....
}

我如何在颤振中实现这一点？

【问题讨论】：

标签： json flutter arraylist

【解决方案1】：

我看过你的json并写了一些代码，只是为了让你知道我已经在本地加载了你的json。

[
    {
        "id": 13,
        "mentor_id": 5,
        "mentee_id": 184,
        "status": null,
        "session_count": 0,
        "current_job": null,
        "email": null,
        "phone_call": null,
        "video_call": null,
        "face_to_face": null,
        "created_at": "2020- 02 - 20 20: 37: 50",
        "updated_at": "2020- 02 - 20 20: 37: 50"
    },
    {
        "id": 14,
        "mentor_id": 8,
        "mentee_id": 184,
        "status": null,
        "session_count": 0,
        "current_job": null,
        "email": null,
        "phone_call": null,
        "video_call": null,
        "face_to_face": null,
        "created_at": "2020- 02 - 21 22: 39: 31",
        "updated_at": "2020- 02 - 21 22: 39: 31"
    }
]

上面是你的 JSON 文件

// To parse this JSON data, do
//
//     final yourDataModel = yourDataModelFromJson(jsonString);

import 'dart:convert';

List<YourDataModel> yourDataModelFromJson(String str) => List<YourDataModel>.from(json.decode(str).map((x) => YourDataModel.fromJson(x)));

String yourDataModelToJson(List<YourDataModel> data) => json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

class YourDataModel {
    int id;
    int mentorId;
    int menteeId;
    dynamic status;
    int sessionCount;
    dynamic currentJob;
    dynamic email;
    dynamic phoneCall;
    dynamic videoCall;
    dynamic faceToFace;
    String createdAt;
    String updatedAt;

    YourDataModel({
        this.id,
        this.mentorId,
        this.menteeId,
        this.status,
        this.sessionCount,
        this.currentJob,
        this.email,
        this.phoneCall,
        this.videoCall,
        this.faceToFace,
        this.createdAt,
        this.updatedAt,
    });

    factory YourDataModel.fromJson(Map<String, dynamic> json) => YourDataModel(
        id: json["id"],
        mentorId: json["mentor_id"],
        menteeId: json["mentee_id"],
        status: json["status"],
        sessionCount: json["session_count"],
        currentJob: json["current_job"],
        email: json["email"],
        phoneCall: json["phone_call"],
        videoCall: json["video_call"],
        faceToFace: json["face_to_face"],
        createdAt: json["created_at"],
        updatedAt: json["updated_at"],
    );

    Map<String, dynamic> toJson() => {
        "id": id,
        "mentor_id": mentorId,
        "mentee_id": menteeId,
        "status": status,
        "session_count": sessionCount,
        "current_job": currentJob,
        "email": email,
        "phone_call": phoneCall,
        "video_call": videoCall,
        "face_to_face": faceToFace,
        "created_at": createdAt,
        "updated_at": updatedAt,
    };
}

这是我为你的 json 制作的模型类

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:sample_project_for_api/model.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  bool _isLoading = false;

  @override
  void initState() {
    super.initState();
    loadYourData();
  }

  Future<String> loadFromAssets() async {
    return await rootBundle.loadString('json/parse.json');
  }

  loadYourData() async {
    String jsonString = await loadFromAssets();
    final yourDataModel = yourDataModelFromJson(jsonString);

    for (int i = 0; i < yourDataModel.length; i++) {
      if (yourDataModel[i].id == 13) {
        print('you got your id');
        // Do your stuff
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(),
    );
  }
}

这是 loadYourData 方法执行核心部分的主文件。

让我知道它是否有效。

【讨论】：

【解决方案2】：

你需要了解更多关于 Dart 语言中的Maps。 Flutter 只是一个制作跨平台应用的框架，它背后的语言和你写的逻辑都是 Dart 语言。




//You have a list of data, so first put it in a List variable.
//You need to first convert the list of raw json objects text response into a list of Maps.
List<Map> data = jsonDecode(httpResponse.body);

//Here we loop through the elements of the list
for (Map jsonObject in data) {

   //This is how you get a value from a Map.
   int id = jsonObject["id"];

   if (jsonObject["id"] == 5){
      print("ID is 5.");
   } else {
      print("ID is NOT 5.");
   }

}

希望这会有所帮助！

【讨论】：