big update to observe, template_binding, polymer

pkg/template_binding/lib/src/node_binding.dart

-// 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 template_binding.src.node_binding;
-
-import 'dart:async' show StreamSubscription;
-import 'dart:html' show Node;
-import 'package:observe/observe.dart' show PathObserver, CompoundPathObserver;
-
-/** Test only method. Not re-exported. */
-getObserverForTest(NodeBinding binding) => binding._observer;
-
-/**
- * A data binding on a [Node].
- * See [NodeBindExtension.bindings] and [NodeBindExtension.bind].
- */
-abstract class NodeBinding {
-  Node _node;
-  var _model;
-
-  // TODO(jmesserly): need common interface for PathObserver,
-  // CompoundPathObserver.
-  var _observer;
-  StreamSubscription _pathSub;
-
-  /** The property of [node] which will be data bound. */
-  final String property;
-
-  /** The property of [node] which will be data bound. */
-  final String path;
-
-  /** The node that has [property] which will be data bound. */
-  Node get node => _node;
-
-  /** The bound data model. */
-  get model => _model;
-
-  /** True if this binding has been [closed]. */
-  bool get closed => _node == null;
-
-  /** The value at the [path] on [model]. */
-  get value => _observer.value;
-
-  set value(newValue) {
-    _observer.value = newValue;
-  }
-
-  NodeBinding(this._node, this.property, this._model, [String path])
-      : path = path != null ? path : '' {
-
-    // Fast path if we're observing "value"
-    if ((model is PathObserver || model is CompoundPathObserver) &&
-        path == 'value') {
-
-      _observer = model;
-    } else {
-      // Create the path observer
-      _observer = new PathObserver(model, this.path);
-    }
-
-    _pathSub = _observer.changes.listen((r) => valueChanged(value));
-    valueChanged(value);
-  }
-
-  /** Called when [value] changes to update the [node]. */
-  // TODO(jmesserly): the impl in template_binding uses reflection to set the
-  // property, but that isn't used except for specific known fields like
-  // "textContent", so I'm overridding this in the subclasses instead.
-  void valueChanged(newValue);
-
-  /** Called to sanitize the value before it is assigned into the property. */
-  sanitizeBoundValue(value) => value == null ? '' : '$value';
-
-  /**
-   * Called by [NodeBindExtension.unbind] to close this binding and unobserve
-   * the [path].
-   *
-   * This can be overridden in subclasses, but they must call `super.close()`
-   * to free associated resources. They must also check [closed] and return
-   * immediately if already closed.
-   */
-  void close() {
-    if (closed) return;
-
-    if (_pathSub != null) _pathSub.cancel();
-    _pathSub = null;
-    _observer = null;
-    _node = null;
-    _model = null;
-  }
-}