Support for observable models, fixes #259

lib/observe/reference.dart

Index: lib/observe/reference.dart
diff --git a/lib/observe/reference.dart b/lib/observe/reference.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f44f0a0d80fc7ec1ba26ee47896759258e278291
--- /dev/null
+++ b/lib/observe/reference.dart
@@ -0,0 +1,32 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library web_ui.observe.reference;
+
+import 'package:web_ui/observe.dart';
+
+/**
+ * An observable reference to an value. Use this if you want to store a single
+ * value. NOTE: it is generally better to use the `@observable` annotation on
+ * your observable class. This class is provided for demonstration purposes, or
+ * if you happen to need a single unnamed observable reference.
+ */
+class ObservableReference<T> {
+  Object _observers;
+  T _value;
+
+  ObservableReference([T initialValue]) : _value = initialValue;
+
+  T get value {
+    if (observeReads) _observers = notifyRead(_observers);
+    return _value;
+  }
+
+  void set value(T newValue) {
+    if (_observers != null && _value != newValue) {
+      _observers = notifyWrite(_observers);
+    }
+    _value = newValue;
+  }
+}