private P getWithUpstreamTracking() {
// this logic should probably go in DerivedValue somehow, except that
// it's only a value and does not know about it's parent property
if (value instanceof DerivedValue) {
// Turn on implicitUpstream, which watches for properties called during value.get.
// Also, keep track if anyone was already tracking derived values so we can put it back.
List<Property<?>> tempUpstream = implicitUpstream;
implicitUpstream = new ArrayList<Property<?>>();
P tempValue = value.get();
List<Property<?>> newUpstream = new ArrayList<Property<?>>(implicitUpstream);
// Put back the previous upstream before we do anything else
implicitUpstream = tempUpstream;
// Only update our upstream properties if they've changed
if (lastUpstream == null || !lastUpstream.equals(newUpstream)) {
ListDiff<Property<?>> diff = ListDiff.of(lastUpstream, newUpstream);
for (Property<?> removed : diff.removed) {
removed.removeDerived(this);
}
for (Property<?> added : diff.added) {
added.addDerived(this);
}
// Remember for change tracking next time
lastUpstream = newUpstream;
}
return tempValue;
} else {
return value.get();
}
}
@Override
protected void fireChanged(List<E> oldValue, List<E> newValue) {
ListDiff<E> diff = ListDiff.of(oldValue, newValue);
for (Location<E> added : diff.added) {
fireEvent(new ValueAddedEvent<E>(added.element));
listenForMemberChanged(added.element);
addToAllValidIfNeeded(added.element);
}
for (Location<E> removed : diff.removed) {
fireEvent(new ValueRemovedEvent<E>(removed.element));
removeFromAllValidIfNeeded(removed.element);
}
fireEvent(new ListChangedEvent<E>(this, oldValue, newValue, diff));
// if someone is listening for "did one of your models change", they
// probably also care about a new model showing up/old model going away
fireEvent(new MemberChangedEvent());
super.fireChanged(oldValue, newValue);
}