Reorganize mdv and observe packages

pkg/mdv/lib/src/template.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.
+
+part of mdv;
+
+/** Extensions to [Element]s that behave as templates. */
+class _TemplateExtension extends _ElementExtension {
+  var _model;
+  _TemplateIterator _templateIterator;
+
+  _TemplateExtension(Element node) : super(node);
+
+  void bind(String name, model, String path) {
+    switch (name) {
+      case 'bind':
+      case 'repeat':
+      case 'if':
+        if (_templateIterator == null) {
+          _templateIterator = new _TemplateIterator(node);
+        }
+        _templateIterator.inputs.bind(name, model, path);
+        return;
+      default:
+        super.bind(name, model, path);
+    }
+  }
+
+  void unbind(String name) {
+    switch (name) {
+      case 'bind':
+      case 'repeat':
+      case 'if':
+        if (_templateIterator != null) {
+          _templateIterator.inputs.unbind(name);
+        }
+        return;
+      default:
+        super.unbind(name);
+    }
+  }
+
+  void unbindAll() {
+    unbind('bind');
+    unbind('repeat');
+    unbind('if');
+    super.unbindAll();
+  }
+
+  /**
+   * Creates an instance of the template.
+   */
+  DocumentFragment createInstance() {
+    var template = node.ref;
+    if (template == null) template = node;
+
+    var instance = _Bindings._createDeepCloneAndDecorateTemplates(
+        template.content, node.attributes['syntax']);
+
+    if (_instanceCreated != null) {
+      _instanceCreated.add(instance);
+    }
+    return instance;
+  }
+
+  /**
+   * The data model which is inherited through the tree.
+   *
+   * Setting this will destructive propagate the value to all descendant nodes,

[justinfagnani, 2013/06/25 23:03:31]

can we do an identity check to avoid churn in some cases?

[Jennifer Messerly, 2013/06/26 23:09:12]

fixed comment. it wasn't accurate (in light of future MDV changes)

+   * and reinstantiate all of the nodes expanded by this template.
+   *
+   * Currently this does not support propagation through Shadow DOMs.
+   */
+  get model => _model;
+
+  void set model(value) {
+    var syntax = TemplateElement.syntax[node.attributes['syntax']];
+    _model = value;
+    _Bindings._addBindings(node, model, syntax);
+  }
+}