Adding data to a json file in dart - json

Question

I have a Json file having some user data as an array , I am able to read those data in my flutter project , But what I wanna do is to add some other user from the data I receive from the textfield in my flutter app.
Can anyone tell me how to do that ? Thanks in advance.
My Json file looks something like this.
{
"users": [
{
"id": 1,
"username": "steve",
"password": "captainamerica"
}
]
}
and I have to add another user with id - 2, username - tony, and password - ironman.

Answer 1

I have tried showing you how to map the JSON to OBJECT and then add a new user to the users object and then to JSON again.
Here's the complete code:
If you have any doubts, please ask:
import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
UsersPodo _usersPodo; // Users object to store users from json
// A function that converts a response body into a UsersPodo
UsersPodo parseJson(String responseBody) {
final parsed = json.decode(responseBody);
return UsersPodo.fromJson(parsed);
}
class Demo extends StatefulWidget {
#override
_Demo createState() => _Demo();
}
class _Demo extends State<Demo> {
final String localJson = '''
{
"users": [
{
"id": 1,
"username": "steve",
"password": "captainamerica"
}
]
}'''; // local json string
Future<UsersPodo> fetchJSON() async {
return compute(parseJson, localJson);
}
Widget body() {
return FutureBuilder<UsersPodo>(
future: fetchJSON(),
builder: (context, snapshot) {
return snapshot.hasError
? Center(child: Text(snapshot.error.toString()))
: snapshot.hasData
? _buildBody(usersList: snapshot.data)
: Center(child: Text("Loading"));
},
);
}
Widget _buildBody({UsersPodo usersList}) {
_usersPodo = usersList;
_usersPodo.users.add(new Users(id: 1, username: "omishah", password: "somepassword")); // add new user to users array
return Text(_usersPodo.users[1].toJson().toString()); // just for the demo output
// use _usersPodo.toJson() to convert the users object to json
}
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Color(0xfff3f3f3),
appBar: AppBar(backgroundColor: Colors.red[900], title: Text("DEMO")),
body: body());
}
}
// PODO Object class for the JSON mapping
class UsersPodo {
List<Users> users;
UsersPodo({this.users});
UsersPodo.fromJson(Map<String, dynamic> json) {
if (json['users'] != null) {
users = new List<Users>();
json['users'].forEach((v) {
users.add(new Users.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
if (this.users != null) {
data['users'] = this.users.map((v) => v.toJson()).toList();
}
return data;
}
}
class Users {
int id;
String username;
String password;
Users({this.id, this.username, this.password});
Users.fromJson(Map<String, dynamic> json) {
id = json['id'];
username = json['username'];
password = json['password'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['id'] = this.id;
data['username'] = this.username;
data['password'] = this.password;
return data;
}
}