public static IObservable <IChangeSet <TCache, TKey> > TransformAndCache <TObject, TKey, TCache>(
this IObservable <IChangeSet <TObject, TKey> > obs,
Func <TKey, TObject, TCache> onAdded,
Action <Change <TObject, TKey>, TCache> onUpdated)
{
var cache = new ChangeAwareCache <TCache, TKey>();
return(obs
.Select(changeSet =>
{
foreach (var change in changeSet)
{
switch (change.Reason)
{
case ChangeReason.Add:
case ChangeReason.Update:
case ChangeReason.Refresh:
var lookup = cache.Lookup(change.Key);
TCache val;
if (lookup.HasValue)
{
val = lookup.Value;
}
else
{
val = onAdded(change.Key, change.Current);
cache.Add(val, change.Key);
}
onUpdated(change, val);
break;
case ChangeReason.Remove:
cache.Remove(change.Key);
break;
case ChangeReason.Moved:
break;
default:
throw new NotImplementedException();
}
}
return cache.CaptureChanges();
})
.Where(cs => cs.Count > 0));
}