Add JSON serializer to every model class?

Question

When it comes to JSON encoding in Dart, per Seth Ladd\'s accouncement the finally approved now official way to go is dart:convert + JSON.Encode.

Answer 1

Some of the answers are no longer applicable to Flutter 2; here is the process for automatically creating toJson and fromJson methods:

https://flutter.dev/docs/development/data-and-backend/json#creating-model-classes-the-json_serializable-way

PS: I wish this would be as simple as using Newtonsoft library in Asp.Net, this solution is closest to an automated solution

Answer 2

Redstone mapper is the best serialization library I've used. JsonObject and Exportable have the downside that you have to extend some of their classes. With Redstone Mapper you can have structures like this

class News
{
    @Field() String title;
    @Field() String text;
    @Field() List<FileDb> images;
    @Field() String link; 
}

It works with getters and setters, you can hide information by not annotating it with @Field(), you can rename field from/to json, have nested objects, it works on the server and client. It also integrates with the Redstone Server framework, where it has helpers to encode/decode to MongoDB.

The only other framework I've seen thats on the right direction is Dartson, but it still lack some features compared to Redstone Mapper.

Answer 3

I have achieve with this:

To make this work, pass explicitToJson: true in the @JsonSerializable() annotation over the class declaration. The User class now looks as follows:

import 'address.dart';
import 'package:json_annotation/json_annotation.dart';
part 'user.g.dart';

@JsonSerializable(explicitToJson: true)
class User {
  String firstName;
  Address address;

  User(this.firstName, this.address);

  factory User.fromJson(Map<String, dynamic> json) => _$UserFromJson(json);
  Map<String, dynamic> toJson() => _$UserToJson(this);
}

You can check here: https://flutter.dev/docs/development/data-and-backend/json#generating-code-for-nested-classes

Answer 4

Another package solving this problem is built_value:

https://github.com/google/built_value.dart

With built_value your model classes look like this:

abstract class Account implements Built<Account, AccountBuilder> {
  static Serializer<Account> get serializer => _$accountSerializer;

  int get id;
  String get name;
  BuiltMap<String, JsonObject> get keyValues;

  factory Account([updates(AccountBuilder b)]) = _$Account;
  Account._();
}

Note that built_value isn't just about serialization -- it also provides operator==, hashCode, toString, and a builder class.

Answer 5

An alternative is to use the Serialization package and add rules for your classes. The most basic form uses reflection to get the properties automatically.

Answer 6

I wrote the Exportable library to solve such things like converting to Map or JSON. Using it, the model declaration looks like:

import 'package:exportable/exportable.dart';

class Customer extends Object with Exportable {
  @export int id;
  @export String name;
}

And if you want to convert to JSON, you may:

String jsonString = customer.toJson();

Also, it's easy to initialize new object from a JSON string:

Customer customer = new Customer()..initFromJson(jsonString);

Or alternatively:

Customer customer = new Exportable(Customer, jsonString);

Please, see the README for more information.