how to convert json string to json object in dart flutter?

Question

I have string like this,

{id:1, name: lorem ipsum, address: dolor set amet}

And I need to convert that string to json, how I can do it in dart flutter? thank you so much for your help.

Answer 1

You have to use json.decode. It takes in a json object and let you handle the nested key value pairs. I'll write you an example

import 'dart:convert';

// actual data sent is {success: true, data:{token:'token'}}
final response = await client.post(url, body: reqBody);

// Notice how you have to call body from the response if you are using http to retrieve json
final body = json.decode(response.body);

// This is how you get success value out of the actual json
if (body['success']) {
  //Token is nested inside data field so it goes one deeper.
  final String token = body['data']['token'];

  return {"success": true, "token": token};
}

Answer 2

Create a model class

class User {
  int? id;
  String? name;
  String? address;

  User({this.id, this.name, this.address});

  User.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    name = json['name'];
    address = json['address'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['name'] = this.name;
    data['address'] = this.address;
    return data;
  }
}

In the logic section

    String data ='{id:1, name: lorem ipsum, address: dolor set amet}';

    var encodedString = jsonEncode(data);

    Map<String, dynamic> valueMap = json.decode(encodedString);
   
    User user = User.fromJson(valueMap);

Also need to import

import 'dart:convert';

Answer 3

You can also convert JSON array to list of Objects as following:

String jsonStr = yourMethodThatReturnsJsonText();
Map<String,dynamic> d  = json.decode(jsonStr.trim());
List<MyModel> list = List<MyModel>.from(d['jsonArrayName'].map((x) => MyModel.fromJson(x)));

And MyModel is something like this:

class MyModel{

  String name;
  int age;

  MyModel({this.name,this.age});

  MyModel.fromJson(Map<String, dynamic> json) {
    name= json['name'];
    age= json['age'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['name'] = this.name;
    data['age'] = this.age;

    return data;
  }
}

Answer 4

 String name =  "{click_action: FLUTTER_NOTIFICATION_CLICK, sendByImage: https://ujjwalchef.staging-server.in/uploads/users/1636620532.png, status: done, sendByName: mohittttt, id: HM11}";
  List<String> str = name.replaceAll("{","").replaceAll("}","").split(",");
  Map<String,dynamic> result = {};
  for(int i=0;i<str.length;i++){
    List<String> s = str[i].split(":");
    result.putIfAbsent(s[0].trim(), () => s[1].trim());
  }
  print(result);
}

Answer 5

You must need to use this sometimes

Map<String, dynamic> toJson() {
  return {
    jsonEncode("phone"): jsonEncode(numberPhone),
    jsonEncode("country"): jsonEncode(country),

 };
}

This code give you a like string {"numberPhone":"+225657869", "country":"CI"}. So it's easy to decode it's after like that

     json.decode({"numberPhone":"+22565786589", "country":"CI"})

Answer 6

value = "{"id":0,"customerId":null,"title":"title"}";   
var response = jsonDecode(value);
print(response['title']);

Answer 7

You must import dart:encode libary. Then use the jsonDecode function, that will produce a dynamic similar to a Map

https://api.dartlang.org/stable/2.2.0/dart-convert/dart-convert-library.html

Answer 8

For converting string to JSON we have to modify it with custom logic, in here first we remove all symbols of array and object and then we split text with special characters and append with key and value(for map). Please try this code snippet in dartpad.dev

import 'dart:developer';

void main() {
  String stringJson = '[{product_id: 1, quantity: 1, price: 16.5}]';

  stringJson = removeJsonAndArray(stringJson);

  var dataSp = stringJson.split(',');
  Map<String, String> mapData = {};
  for (var element in dataSp) {
    mapData[element.split(':')[0].trim()] = element.split(':')[1].trim();
  }

  print("jsonInModel: ${DemoModel.fromJson(mapData).toJson()}");
}

String removeJsonAndArray(String text) {
  if (text.startsWith('[') || text.startsWith('{')) {
    text = text.substring(1, text.length - 1);
    if (text.startsWith('[') || text.startsWith('{')) {
      text = removeJsonAndArray(text);
    }
  }
  return text;
}

class DemoModel {
  String? productId;
  String? quantity;
  String? price;

  DemoModel({this.productId, this.quantity, this.price});

  DemoModel.fromJson(Map<String, dynamic> json) {
    log('json: ${json['product_id']}');
    productId = json['product_id'];
    quantity = json['quantity'];
    price = json['price'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = <String, dynamic>{};
    data['product_id'] = productId;
    data['quantity'] = quantity;
    data['price'] = price;
    return data;
  }
}