json2object 2.4.2

Initialize object directly from json with macro

Released 2017-05-05.

To install, run:

haxelib install json2object 2.4.2

See using Haxelib in Haxelib documentation for more information.

Current version2.4.2
StatisticsInstalled 88 times
Tags cross, json, macro


json2object - Initialize object directly from json

Build Status

This library uses macro and a typed position aware JSON parsing (hxjsonast : https://github.com/nadako/hxjsonast/) to create a parser from json to every supported object.

Incorrect json files or mismatch between the object and the json will yield errors or exceptions, with information on the position of the problematic parts.

Requires at least haxe 3.3.0-rc.1.


haxelib install json2object


Using the parser

var parser = new json2object.JsonParser<Cls>(); // Creating a parser for Cls class
parser.fromJson(jsonString, filename); // Parsing a string. A filename is specified for errors management
var data:Cls = parser.value; // Access the parsed class
var errors:Array<json2object.Error> = parser.errors; // Access the potential errors yield during the parsing

It is also possible to populate an existing Array with the errors

var errors = new Array<json2object.Error>();
var data:Cls = new json2object.JsonParser<Cls>(errors).fromJson(jsonString, filename);

To print the errors, you can do


Constraints in the parsing

  • Variables defined with the @:jignored metadata will be ignored by the parser.
  • Variables defined with the @:optional metadata won't trigger errors if missing.
  • Private variables are ignored.

Supported types

  • Basic types (Int, Float, Bool, String)
  • Null and Array
  • Map with Int or String keys
  • Class (generics are supported)
  • Anonymous structure
  • Typedef alias of supported types
  • Enum values
  • Abstract over a supported type
  • Abstract enum of String, Int, Float or Bool


  • As of version 2.4.0, the parser fields warnings and object have been replaced by errors and value respectively. Previous notations are still supported.

  • Anonymous structure variables can be defined to be loaded with a default value if none is specified in the json using the @:default metadata

typedef Struct = {
	var normal:String;

	@:default(new Map<Int, String>())
	var map:Map<Int,String>;

	@:default(-1) @:optional
	var id:Int;
  • Variable defined as (default, null) may have unexpected behaviour on some extern classes.

  • You can alias a field from the json into another name, for instance if the field name isn't a valid haxe identifier.

typedef Struct = {
	@:alias("public") var isPublic:Bool;
class Main {
	static function main() {
		var parser = new JsonParser<Struct>();
		var data = parser.fromJson('{"public": true }', "file.json");

If multiple alias metadatas are on the variable only the last one is taken into account.


With an anonymous structure:

import json2object.JsonParser;

class Main {
	static function main() {
		var parser = new JsonParser<{ name : String, quantity : Int }>();
		var data = parser.fromJson('{"name": "computer", "quantity": 2 }', "file.json");
		trace(data.name, data.quantity);

A more complex example with a class and subclass:

import json2object.JsonParser;

class Data {
	public var a:String;
	public var b:SubData;
	public var d:Array<Int>;
	public var e:Array<Map<String, String>>;
	public var f:Array<Float>;
	public var g:Array<Bool>;
	public var h:Math;

	public function new() {

class SubData {
	public var c:String;

	public function new() {

class Main {
	static function main() {
		var parser = new JsonParser<Data>();
		var data = parser.fromJson('{"a": "a", "b": {"c": "c"}, "e": [ { "c": "1" }, { "c": "2" } ], "f": [], "g": [ true ] }', "file.json");
		var errors = parser.errors;


		for (e in data.e) {


		for (g in data.g) {

		for (e in errors) {
			switch(e) {
				case IncorrectType(variable, expected, pos):
				case UninitializedVariable(variable, pos):
				case UnknownVariable(variable, pos):