Leksat / dart-exportable

Exportable mixin that provides an easy way to export/import Dart objects to/from Maps or JSON.

The library provides the Exportable class - a mixin providing an ability to export objects to Maps or JSON. Useful for data models: storing in databases as Maps, or passing between client/server as JSON.

Properties of a class that is mixed with Exportable and wanted to be exportable should be annotated with @export, and could be

• any type supported by JSON (see JsonEncoder.convert())
• any calss that mixes Exportable
• DateTime

Usage example:

class Foo extends Object with Exportable {
  @export String bar;
}

void main() {
  Foo foo = new Exportable(Foo);
  // The same as
  // Foo foo = new Foo();
  foo.bar = 'Bar';
  print(foo.toMap());
  // => {bar: Bar}
  print(foo.toJson());
  // => {"bar":"Bar"}
  print(foo.toString());
  // => {"bar":"Bar"}
  Foo baz = new Exportable(Foo, '{"bar":"Baz"}');
  // The same as
  // Foo baz = new Foo();
  // baz.initFromJson('{"bar":"Baz"}');
  print(baz);
  // => {"bar":"Baz"}
  Foo baz2 = new Exportable(Foo, {'bar': 'Baz'});
  // The same as
  // Foo baz2 = new Foo();
  // baz2.initFromMap({'bar': 'Baz'});
  print(baz2);
  // => {"bar":"Baz"}
}

Metadata: Dart VM vs dart2js

Metadata annotations are used to

• let the Exportable class know which properties could be exported or imported,
• allow tree-shaking of a code.

When running in JS context, there are some difficulties with type detecting. So, here are some annotation rules.

If you plan to use exportable models with Dart VM only:

• Each exportable property of an exportable class should be annotated with @export.
• If you need a tree-shaking: annotate an exportable class itself. But this is not mandatory.

If you plan to use exportable models with dart2js:

• Each exportable property of a JSON supported class should be annotated with @export.
• Properties of a non JSON supported class (see JsonEncoder.convert()) should be annotated with @Export(<type>), where <type> is a type of a property.
• Exportable class itself should be annotated with @export.

TODO

• Provide more information/examples in the README.
• Check why dart2js says "Hint: X methods retained for use by dart:mirrors out of X total methods (X%)" (seems like we have 1 retained method for one exportable class... is this a constructor?)
• Write tests!