An experiment in using mirrors to convert from a map to a model and vice versa.

Mirrors are a way of performing reflection in Dart. This permits an unknown class to be traversed and information about fields, properties and methods to be extracted, which is particularly useful if you wish to convert a serialized representation of an object such as JSON into an actual object instance.

Mirrors are now properly supported in dart2js, so model_map will work even if compiled to javascript as long as you decorate your entity with @reflectable.

At this stage ModelMap only worries about non-static, public fields and will ignore getters and setters.

import 'package:model_map/model_map.dart';

class SimpleModel extends ModelMap
{
  String string;
  int integer;
  bool flag;
  num float;
}

main()
{
  var map   = { 'string': 'some text', 'integer': 42, 'flag': true, 'float': 1.23 };
  var model = new SimpleModel().fromMap(map);

  // The model is populated and ready to use at this point
}

You can also take an existing model and convert it to a map

// A map of <String, dynamic>
var map = model.toMap();

A couple of utility functions are included that simply wrap fromMap and toMap using the built-in parse and stringify capabilities so that you can simply call fromJson and toJson on your model instance.

Now that dart2js supports enough of the mirror system, ModelMap will work in a javascript application. One thing to be aware of is that dart2js performs tree shaking and to ensure that your entities can be mirrored properly when compiled to javascript you should decorate them with a helper attribute:

@reflectable
class SimpleModel extends ModelMap
{
  String string;
  int integer;
}

ModelMap can support model instances within models, but they must all extend the ModelMap class. It also handles List and Map collections (maps are limited to string keys only, since this is all that JSON can use).

import 'package:model_map/model_map.dart';

class ComplexModel extends ModelMap
{
  int integer;
  SimpleModel simple;
  List<SimpleModel> modelList;
  Map<String, DateTime> dateMap;
  Map<String, SimpleModel> modelMap;
  Map<String, List<SimpleModel>> modelListMap;
}

main()
{
  var json  = getJsonFromServer();
  var model = new ComplexModel().fromJson(json);

  print(model.modelMap['a key'].flag);
}

ModelMap should cope with reasonably complex object trees.

When converting to JSON or a map, ModelMap will always convert dates to an ISO 8601 string, however when parsing a map it will accept an ISO 8601 string or an integer representing UTC unix time.