Proposal for computed properties in Dart. Whenever `firstName` or `lastName` changes, I want `fullName` to also dispatch a change event. This'll be very useful for binding a read-only property in WebUI. Right now, I have to write some ugly boilerplate to get this to work. Ideally there'd be a way to set this up through metadata.

gistfile1.dart

// Assumes that we're using mdv_observe

// Verbose way
class Person extends ObservableBase {
  
  @observable
  String firstName;
  
  @observable
  String lastName;
  
  String get fullName => '${firstName} ${lastName}';
  
  void notifyPropertyChange(Symbol field, Object oldValue, Object newValue) {
    super.notifyPropertyChange(field, oldValue, newValue);
    
    if (field == new Symbol('lastName') || field == new Symbol('firstName')) {
      notifyPropertyChange(new Symbol('fullName'), null, fullName);
    }
  }
  
}

// Metadata approach
// @computed is used to annotate [fullName] to dispatch a change event whenever [firstName] or [lastName] changes.
class Person extends ObservableBase {
  
  @observable
  String firstName;
  
  @observable
  String lastName;
  
  @computed ['firstName', 'lastName']
  String get fullName => '${firstName} ${lastName}';
  
}