CODEWITHSUNDEEP
flutterdart
macphail magwira
macphail magwira

Reputation: 191

Failing to use .toJson() function on a List with maps in flutter dart

I have a list made up of maps in the following format below

List<dynamic> data = [];


 data = [
  {'name': 'Name', type: 'STRING',},
  {'name': 'Age', type: 'INTEGER'},
  {'name': 'Weight', type: 'FLOAT'},
  {'name': 'IsMagic', type: 'BOOLEAN'},
];

I am trying to send it over the internet in JSON format by using the .toJson() but i keep getting the error

The method 'toJson' isn't defined for the type 'List'.

this was how i went about it

Future creatingTable() async {
    var url = Uri.parse(
        'https://us-central1-denance-cbf3f.cloudfunctions.net/api/create_table');
    var response =
        await http.post(
            url,
            body: data.toJson(),
            headers: < String, String > {
                'Content-Type': 'application/json; charset=UTF-8',
            },
        );
    print(
        'Response status: ${response.statusCode}');
    print(
        'Response body: ${response.body}');
}

how do i resolve the problem?

Upvotes: 0

Views: 2686

Answers (3)

Erkin Kurt
Erkin Kurt

Reputation: 663

Actually the error says it all. List class doesn't have toJson method defined in it. toJson and fromJson methods are functions that we define to regarding classes as developers. For example an entity like Car can have these methods.

class Car {
  final String brand;

  Car({this.brand});

  Map<String, dynamic> toJson() => {'brand': brand};

  factory Car.fromJson(Map<String, dynamic> json) => 
    Car(brand: json['brand']);
}

For your question's answer, if you want to pass the array directly as a json, what you can do is pass data to jsonEncode function from dart:convert and it will convert your array to json string. Usage: jsonEncode(data).

Upvotes: 0

hexakosio
hexakosio

Reputation: 16

Try to use jsonEncode from dart:convert

List<dynamic> data = [];

data = [
   {'name': 'Name', 'type': 'STRING',},
   {'name': 'Age', 'type': 'INTEGER'},
   {'name': 'Weight', 'type': 'FLOAT'},
   {'name': 'IsMagic', 'type': 'BOOLEAN'},
];

dynamic body = jsonEncode(data);

Upvotes: 0

Luca Oropallo
Luca Oropallo

Reputation: 519

You should import 'dart:convert' and use jsonEncode(data):

import 'dart:convert';

Future creatingTable() async {
    var url = Uri.parse(
        'https://us-central1-denance-cbf3f.cloudfunctions.net/api/create_table');
    var response =
        await http.post(
            url,
            body: jsonEncode(data),
            headers: {
              HttpHeaders.contentTypeHeader: 'application/json',
            },
        );
    print(
        'Response status: ${response.statusCode}');
    print(
        'Response body: ${response.body}');
}

Upvotes: 1

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