JSON to Dart class (Flutter)

How to use it

1. Enter json input and root type name.
2. The result appears straight away and updates as you edit.
3. Copy the result, or copy a link that keeps the same values to share it.

How it is calculated

int, double, String, bool, List<T> and dynamic, with a class per object. null or a missing key makes the type nullable, such as int?. Numbers are read through num and then toInt or toDouble, because JSON may send 10 instead of 10.0, and nested objects use their own fromJson.

Example

Inputs: Root type name = Root. Result: Generated code: class Root { final int id; final String name; final String email; final bool isActive; final double balance; final List<String> tags; final Address address; final List<Order> orders; Root({ required this.id, required this.name, required this.email, required this.isActive, required this.balance, required this.tags, required this.address, required this.orders, }); factory Root.fromJson(Map<String, dynamic> json) => Root( id: (json['id'] as num).toInt(), name: json['name'] as String, email: json['email'] as String, isActive: json['is_active'] as bool, balance: (json['balance'] as num).toDouble(), tags: (json['tags'] as List<dynamic>).map((e) => e as String).toList(), address: Address.fromJson(json['address'] as Map<String, dynamic>), orders: (json['orders'] as List<dynamic>).map((e) => Order.fromJson(e as Map<String, dynamic>)).toList(), ); Map<String, dynamic> toJson() => { 'id': id, 'name': name, 'email': email, 'is_active': isActive, 'balance': balance, 'tags': tags, 'address': address.toJson(), 'orders': orders.map((e) => e.toJson()).toList(), }; } class Address { final String city; final String postalCode; Address({ required this.city, required this.postalCode, }); factory Address.fromJson(Map<String, dynamic> json) => Address( city: json['city'] as String, postalCode: json['postal_code'] as String, ); Map<String, dynamic> toJson() => { 'city': city, 'postal_code': postalCode, }; } class Order { final String orderId; final double total; final String? coupon; Order({ required this.orderId, required this.total, this.coupon, }); factory Order.fromJson(Map<String, dynamic> json) => Order( orderId: json['order_id'] as String, total: (json['total'] as num).toDouble(), coupon: json['coupon'] as String?, ); Map<String, dynamic> toJson() => { 'order_id': orderId, 'total': total, 'coupon': coupon, }; }; Types generated: 3; Fields: 13.

{
  "id": 1024,
  "name": "Sara Ahmed",
  "email": "sara@example.com",
  "is_active": true,
  "balance": 1520.75,
  "tags": ["vip", "riyadh"],
  "address": { "city": "Riyadh", "postal_code": "12211" },
  "orders": [
    { "order_id": "A-1", "total": 99.5, "coupon": "EID10" },
    { "order_id": "A-2", "total": 120, "coupon": null }
  ]
}

class Root {
  final int id;
  final String name;
  final String email;
  final bool isActive;
  final double balance;
  final List<String> tags;
  final Address address;
  final List<Order> orders;

  Root({
    required this.id,
    required this.name,
    required this.email,
    required this.isActive,
    required this.balance,
    required this.tags,
    required this.address,
    required this.orders,
  });

  factory Root.fromJson(Map<String, dynamic> json) => Root(
        id: (json['id'] as num).toInt(),
        name: json['name'] as String,
        email: json['email'] as String,
        isActive: json['is_active'] as bool,
        balance: (json['balance'] as num).toDouble(),
        tags: (json['tags'] as List<dynamic>).map((e) => e as String).toList(),
        address: Address.fromJson(json['address'] as Map<String, dynamic>),
        orders: (json['orders'] as List<dynamic>).map((e) => Order.fromJson(e as Map<String, dynamic>)).toList(),
      );

  Map<String, dynamic> toJson() => {
        'id': id,
        'name': name,
        'email': email,
        'is_active': isActive,
        'balance': balance,
        'tags': tags,
        'address': address.toJson(),
        'orders': orders.map((e) => e.toJson()).toList(),
      };
}

class Address {
  final String city;
  final String postalCode;

  Address({
    required this.city,
    required this.postalCode,
  });

  factory Address.fromJson(Map<String, dynamic> json) => Address(
        city: json['city'] as String,
        postalCode: json['postal_code'] as String,
      );

  Map<String, dynamic> toJson() => {
        'city': city,
        'postal_code': postalCode,
      };
}

class Order {
  final String orderId;
  final double total;
  final String? coupon;

  Order({
    required this.orderId,
    required this.total,
    this.coupon,
  });

  factory Order.fromJson(Map<String, dynamic> json) => Order(
        orderId: json['order_id'] as String,
        total: (json['total'] as num).toDouble(),
        coupon: json['coupon'] as String?,
      );

  Map<String, dynamic> toJson() => {
        'order_id': orderId,
        'total': total,
        'coupon': coupon,
      };
}

Limits and caveats

• It does not use json_serializable or freezed, so the code stands alone without build_runner.
• A key that is not a valid name becomes camelCase, and the original key stays inside fromJson and toJson.