+ private class LazyArtist extends DefaultArtist {
+
+ private final Memoizer<Void> tracks = new Memoizer<Void>(new Callable<Void>() {
+ public Void call() throws DatabaseException {
+ if (!hasValue("tracks")) {
+ value("tracks", Collection.class).set(getTracksByArtist(id()));
+ }
+ return null;
+ }
+ });
+
+ public LazyArtist(String id) {
+ super(id);
+ }
+
+ public Collection<Track> tracks() {
+ tracks.get();
+ return super.tracks();
+ }
+
+ }
+