How to decode JSON in Flutter?

Just use

json.decode()

or

jsonDecode()

In Dart 2 all screaming-case constants were changed to lower-camel-case.

Ensure to import 'dart:convert';

You need to use import 'dart:convert';

Decode : JsonDecoder().convert("$response");

Encode : JsonEncoder().convert(object)

You will need to import dart:convert:

import 'dart:convert';

Inline example

String rawJson = '{"name":"Mary","age":30}';

Map<String, dynamic> map = jsonDecode(rawJson); // import 'dart:convert';

String name = map['name'];
int age = map['age'];

Person person = Person(name, age);

Note: When I was doing this in VS Code for server side Dart I had to specify the type:

Map<String, dynamic> map = jsonDecode(rawJson) as Map<String, dynamic>;

Model class example

The model class includes the map conversion logic:

class Person {
  String name;
  int age;
  Person(this.name, this.age);

  // named constructor
  Person.fromJson(Map<String, dynamic> json)
      : name = json['name'],
        age = json['age'];

  // method
  Map<String, dynamic> toJson() {
    return {
      'name': name,
      'age': age,
    };
  }
 
}

And the JSON conversion is done like this:

String rawJson = '{"name":"Mary","age":30}';
Map<String, dynamic> map = jsonDecode(rawJson);
Person person = Person.fromJson(map);

See my full answer here.

Generating the serialization code

It is easy to make errors when writing the serialization code, so it is generally recommended to use the json_serializable package by the Dart Team. However, you can read about the pros and cons of the different methods here.

If you want even more options you can also check out the built_value package.

See also

• Work with JSON in Flutter - Part 1: dart:convert
• Work with JSON in Flutter - Part 2: json_serializable
• Some Options for Deserializing JSON with Flutter