delegate.dart

abstract class Person {
  String name;
  String address;
}

class DelegatorPerson implements Person {
  DelegateePerson delegatee;
  DelegatorPerson(this.delegatee);
  String get name => delegatee.name(this);
  set name(String value) => delegatee.nameSet(this, value);
  String get address => delegatee.address(this);
  set address(String value) => delegatee.addressSet(this, value);
  toString() => "$name, $address";
}

abstract class DelegateePerson {
  DelegateePerson next;
  DelegateePerson(this.next);
  String name(Person self);
  void nameSet(Person self, String value);
  String address(Person self);
  void addressSet(Person self, String value);
}

class DelegateeAddress extends DelegateePerson {
  String _address;
  DelegateeAddress(DelegateePerson next, this._address): super(next);
  String name(self) => next != null ? next.name(self) : throw "'name' unimplemented";
  void nameSet(self, value) => next != null ? next.nameSet(self, value) : throw "'name=' unimplemented";
  String address(self) => _address;
  void addressSet(self, value) => _address = value;
}

class DelegateeName extends DelegateePerson {
  String _name;
  DelegateeName(DelegateePerson next, this._name): super(next);
  String name(self) => _name;
  void nameSet(self, value) => _name = value;
  String address(self) => next != null ? next.address(self) : throw "'address' unimplemented";
  void addressSet(self, value) => next != null ? next.addressSet(self, value) : throw "'address=' unimplemented";
}

void main() {
  var house = DelegateeAddress(null, "5th Anevue");
  var adamName = DelegateeName(house, "Adam");
  var eveName = DelegateeName(house, "Eve");
  var adam = DelegatorPerson(adamName);
  var eve = DelegatorPerson(eveName);
  print("$eve & $adam.");
  eve.address = "Broadway";
  print("$eve & $adam.");
}