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

[Matthew Hall <matthall@xxxxxxxxxxxxxxxxx>]

Pierre Francis Roy wrote:
> Required in my situation
> IObservableMap[] map = new IObservableMap[3];
> ..
> IEMFValueProperty prop =  
> EMFProperties.value(DairyStudioQualityPackage.Literals.SAMPLE_SET__SAMPLES); 
>
> ??? map[2] = new NotifyingListSizeProperty().observe(prop); ???

You can make a nested property as follows:

IEMFValueProperty eListSizeProp = EMFProperties
    .value(DairyStudioQualityPackage.Literals.SAMPLE_SET__SAMPLES)
    .value(new NotifyingListSizeProperty());

Assuming you are binding this property to a JFace viewer, your code 
would be something like:

IObservableSet knownElements =
    observableListContentProvider.getKnownElements();
map[2] = eListSizeProperty.observeDetail(knownElements);

I've also been thinking that we should provide a property reducer method 
for collection properties:

interface IListProperty {
+ public IValueProperty reduce(IValueProperty)
}

interface ISetProperty {
+ public IValueProperty reduce(IValueProperty)
}

interface IMapProperty {
+ public IValueProperty reduce(IValueProperty)
}

This way we could just provide a generic property Properties.size(), thus:

IValueProperty listSizeProp = EMFProperties
    .list(DairyStudioQualityPackage.Literals.SAMPLE_SET__SAMPLES)
    .reduce(Properties.size());

We could also include several generic reducer properties like average, 
median, sum, min, max, etc.  What do you think?

Matthew