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JSON conversion in Flutter and Dart

A quick reference with examples

Article updated July 4, 2023 for Dart 3.

The article Parsing Complex JSON in Flutter is very good, but I was looking for something shorter, a quick reference with examples.

If I have a simple JSON string like this:

{
    "name" : "Mary",
    "age" : 30
}

How do I convert it to a Dart object? Or a Dart object to JSON?

Setup

Import the builtin convert library, which includes the jsonDecode() and jsonEncode() methods:

import 'dart:convert';

I will use the class below in the following examples:

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

And while it isn’t absolutely necessary, I’m also using the strict typing rules in analysis_options.yaml. This lets the analyzer warn you when you might forget about dynamic and object types.

include: package:lints/recommended.yaml

analyzer:
  language:
    strict-casts: true
    strict-raw-types: true

This uses the standard lints package in pubspec.yaml:

dev_dependencies:
  lints: ^2.0.0

Method 1: Direct conversion