method openPropertyObserver

Source

void openPropertyObserver() {
  if (_propertyObserver != null) {
    _propertyObserver.open(notifyPropertyChanges);
  }

  // Dart note: we need an extra listener only to continue supporting
  // @published properties that follow the old syntax until we get rid of it.
  // This workaround has timing issues so we prefer the new, not so nice,
  // syntax.
  if (_element._publish != null) {
    changes.listen(_propertyChangeWorkaround);
  }
}