json_conv

json_conv started as a fork of json_god to add Annotation Support.

Most of the source has been rewritten since the initial fork.

Decoding of json Strings compared to Dartson and json_god:

JSON.decode took: 741ms
json_conv took: 3495ms
json_conv map took: 7583ms
json_god took: 9474ms
dartson took: 42433ms

Installation

dependencies:
  json_conv: 
    git:
      url: git://github.com/Kemonozume/json_conv.git
      ref: 653b2d2fdb795de933e317cd416b40d1b31902ac

Usage

import 'package:json_conv/json_conv.dart'

@Conv()
class ListComplex {
  List<ExtendeeClass> list;
}

@Conv()
class ExtendeeClass {
  int id;
  String text;
}

void main() {
    final json =
              '{"list": [{"id":0, "text":"0"}, {"id":1, "text":"1"},{"id":2, "text":"2"}]}';
    final object = decode(json, ListComplex);
    print(encode(object));
}

Check out the Tests to see how to use json_conv.

Dart2JS Compatibility

json_conv does not support Transformers for now and you need to use @MirrorUsed. @MirrorsUsed documentation can be found here.

Example on how to use the mirrors import:

@MirrorsUsed(metaTargets: const [Conv])
import 'dart:mirrors';

import 'package:json_conv/json_conv.dart';

@Conv()
class ExtendeeClass {
  int id;
  String text;
}

The @Conv Annotation is only used to tell mirrors what classes are being used. You only need the @Conv Annotation for Dart2JS Compatibility and can safely be omitted if you are using the DartVM.

Property Annotation

The @Property Annotation lets you rewrite JSON keys and actively ignore properties.

class AnnotationSample {
  int id;

  @Property(name: "test")
  String text;

  AnnotationSample();
}

void main() {
    final json = '{"id":1, "test":"test text"}';
    final sample = conv.decode(json, AnnotationSample);
    print(sample.text);
}

Implementation Annotation

The @Implementation Annotation enables you to use abstract classes in your JSON Data Structure and specify the Implementation of the abstract class with the help of the Annotation.

abstract class Person {
  int id;
  String name;
}

@Conv()
class Professor extends Person {
  String faculty;
}

@Conv()
class Response {
  @Implementation(Professor)
  Person person;
}

void main() {
    final json =
            '{"person":{"id": 0, "name":"test professor", "faculty":"test fac"}}';
    final p = decode(json, Response);

    print(p.person.faculty); //prints test fac
}

TypeSeeker Annotation

The @TypeSeeker Annotation enables you to specify the Type that should be used mid-parsing. You can specify what JSON Key you want to use to specify the Type of the generated object.

It is not possible yet to get the entire object.

@Conv()
abstract class Channel {
  int id;
  String type;
}

@Conv()
class TextChannel extends Channel {
  String topic;
}

@Conv()
class VoiceChannel extends Channel {
  int bitrate;
}

@Conv()
class ResponseChannel {
  @TypeSeeker("type", seekChannel)
  List<Channel> channel;
}

Type seekChannel(dynamic val) {
  if (val == "text") {
    return TextChannel;
  } else if (val == "voice") {
    return VoiceChannel;
  } else {
    print("unknown type $val");
    return null; //will throw an StateError
  }
}

void main() {
    final json =
        '{"channel": [{"id":0, "type":"text", "topic":"test topic"}, {"id":1, "type":"voice", "bitrate":65000}]}';
    final c = decode(json, ResponseChannel);
}

TypeTransformer interface

The TypeTransformer<T> Interface allows you to encode and decode a specific Type how you want.

class _DateTransformer extends TypeTransformer<DateTime> {
  @override
  DateTime decode(dynamic value) {
    try {
      return DateTime.parse(value);
    } catch (e, st) {
      return null;
    }
  }

  @override
  String encode(DateTime value) {
    if (value == null) return "null";
    return value.toIso8601String();
  }
}

After creating a TypeTransformer you have to register the Transformer using the function void registerTransformer(TypeTransformer t, Type type).

Roadmap

• preserve order of lists
• transformer for better Dart2JS compatibility
• better exceptions

Credits

The TypeTransformer Interface and the Property Annotation were written by eredo.