[news.eclipse.tools.emf] Re: Observing EList size

[Matthew Hall <matthall@xxxxxxxxxxxxxxxxx>]

Pierre Francis Roy wrote:
> In this case what I want to do is to observ the size of that EList 
> (EList.size()).

If there is an EStructuralFeature for EList.size() somewhere then you 
could observe it using:
    EMFProperties.value(eListSizeStructuralFeature).observe(eList)

Otherwise you can write a custom IValueProperty:

class NotifyingListSizeProperty extends SimpleValueProperty {
  protected Object doGetValue(Object source) {
    return ((NotifyingList)source).size();
  }

  protected void doSetValue(Object source, Object value) {
    throw new UnsupportedOperationException(
        toString() + " is unmodifiable");
  }

  public INativePropertyListener adaptListener(
      ISimplePropertyListener listener) {
    return new Listener(listener);
  }

  private class Listener extends AdapterImpl
        implements INativePropertyListener {
    ISimplePropertyListener delegate;

    public Listener(ISimplePropertyListener delegate) {
      this.delegate = delegate;
    }

    public void addTo(Object source) {
      if (source != null)
        ((Notifier) ((NotifyingList)source).getNotifier())
             .eAdapters().add(this);
    }

    public void removeFrom(Object source) {
      if (source != null)
        ((Notifier) ((NotifyingList)source).getNotifier())
             .eAdapters().remove(this);
    }

    public void notifyChanged(Notification msg) {
      delegate.handleEvent(new SimplePropertyEvent(
          SimplePropertyEvent.CHANGE,
          msg.getNotifier(),
          NotifyingListenerProperty.this,
          null);
    }
  }

  public String toString() { return "EList.size <int>"; }
}

With this property you can basically do the same the first example code:

IObservableValue listSize =
    new NotifyingListSizeProperty().observe(eList);