One attempt at a Persistable mixin in Dart.

persistable.dart

import 'dart:mirrors';
import 'dart:async';

// TODO: inject the persistance storage driver
abstract class Persistable {
  int _dbId;
  
  static const constructor = const Symbol('fromPersistance');
  
  static Future load(int id, Type type) {
    // Magically pretend to get this from a Database.
    var data = {'id': 1, 'firstName': 'Bob', 'lastName': 'Smith'};
    
    var classMirror = reflectClass(type);
    
    // See dartbug.com/11161
    if (classMirror.constructors[new Symbol('$type.fromPersistance')] == null) {
      throw '$type should have a constructor $constructor';
    }
    
    var instance = classMirror.newInstance(constructor, [data]);
    var object = instance.reflectee;
    
    // Mixins can't have constructors, so I set the ID here.
    // Not sure if there's a better way.
    object._dbId = data['id'];
    
    // A real DB would use a Future-based API.
    return new Future.value(object);
  }
  
  Future store() {
    var map = toMap();
    
    // Magically do the query here with the map of fields.
    // Use dbId to identify the object.
                
    return new Future.value(true);
  }
  
  Future<int> create() {
    if (dbId != null) {
      throw 'Already has as ID of $dbId';
    }
    
    // Tnsert into database, get ID.
    
    _dbId = 100;
    
    return new Future.value(dbId);
  }
  
  Map toMap();
  
  // This assumes there's no reason for code to change an ID.
  int get dbId => _dbId;
}

class Person extends Object with Persistable {
  String firstName;
  String lastName;
  
  Person(this.firstName, this.lastName);
  
  Person.fromPersistance(Map data) {
    firstName = data['firstName'];
    lastName = data['lastName'];
  }
  
  Map toMap() => {'firstName': firstName, 'lastName': lastName};
  
  String toString() => '$dbId $firstName $lastName';
}

void main() {
  var p = new Person('Bob', 'Smith');
  
  p.create()
      .then((id) => print(id))
      .then((_) => Persistable.load(p.dbId, Person))
      .then((newP) => p = newP)
      .then((_) {
        p.firstName = 'Alice';
        return p.store();
      })
      .then((_) => print('completed store'))
      .catchError(print);
  
//  Persistable.load(1, Person)
//    .then((Person p) {
//      print(p);
//      p.firstName = 'Alice';
//      return p.store();
//    })
//    .then((_) => print('completed store'))
//    .catchError(print);
}