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Unified Diff: pkg/polymer/lib/src/property_accessor.dart

Issue 420673002: Roll polymer packages to version 0.3.4 (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: Created 6 years, 5 months ago
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Index: pkg/polymer/lib/src/property_accessor.dart
diff --git a/pkg/polymer/lib/src/property_accessor.dart b/pkg/polymer/lib/src/property_accessor.dart
new file mode 100644
index 0000000000000000000000000000000000000000..84e1bc9da26b693902a3f5288b48a1949fc3e9bf
--- /dev/null
+++ b/pkg/polymer/lib/src/property_accessor.dart
@@ -0,0 +1,66 @@
+// 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.
+
+/// Code for property accessors from declaration/properties.js
+part of polymer;
+
+// Dart note: this matches the property defined by createPropertyAccessor in
+// polymer-dev/src/declarations/properties.js. Unlike Javascript, we can't
+// override the original property, so we instead ask users to write properties
+// using this pattern:
+//
+// class Foo extends PolymerElement {
+// ...
+// @published
+// get foo => readValue(#foo);
+// set foo(v) { writeValue(#foo, v); }
+//
+// and internally readValue/writeValue use an instance of this type to
+// implement the semantics in createPropertyAccessor.
+class _PropertyAccessor<T> {
+ // Name of the property, in order to properly fire change notification events.
+ final Symbol _name;
+
+ /// The underlying value of the property.
+ T _value;
+
+ // Polymer element that contains this property, where change notifications are
+ // expected to be fired from.
+ final Polymer _target;
+
+ /// Non-null when the property is bound.
+ Bindable bindable;
+
+ _PropertyAccessor(this._name, this._target, this._value);
+
+ /// Updates the underlyling value and fires the expected notifications.
+ void updateValue(T newValue) {
+ var oldValue = _value;
+ _value = _target.notifyPropertyChange(_name, oldValue, newValue);
+ _target.emitPropertyChangeRecord(_name, oldValue, newValue);
jakemac 2014/07/25 16:40:33 I noticed that newValue and oldValue are swapped h
Siggi Cherem (dart-lang) 2014/07/25 17:45:12 good catch! I swapped them subconsciously because
+ }
+
+ /// The current value of the property. If the property is bound, reading this
+ /// property ensures that the changes are first propagated in order to return
+ /// the latest value. Similarly, when setting this property the binding (if
+ /// any) will be updated too.
+ T get value {
+ if (bindable != null) bindable.deliver();
+ return _value;
+ }
+
+ set value(T newValue) {
+ if (bindable != null) {
+ bindable.value = newValue;
+ } else {
+ updateValue(newValue);
+ }
+ }
+
+ toString() {
+ var name = smoke.symbolToName(_name);
+ var hasBinding = bindable == null ? '(no-binding)' : '(with-binding)';
+ return "[$runtimeType: $_target.$name: $_value $hasBinding]";
+ }
+}

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