Fix ObservableMap.cast/retype. (#64)
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 88e1ba3..9636dfb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,10 @@
+## 0.22.0
+
+* Added `ObservableMap.castFrom`, similar to `Map.castFrom`.
+
+* Fixed a bug where `ObservableMap`'s `cast` and `retype` function would create
+ a new empty instance instead of a forwarding instance.
+
## 0.21.3
* Support Dart 2 collection methods where previously threw `UnimplementedError`.
diff --git a/lib/src/observable_map.dart b/lib/src/observable_map.dart
index 4f43d13..b5c1f1b 100644
--- a/lib/src/observable_map.dart
+++ b/lib/src/observable_map.dart
@@ -20,6 +20,39 @@
/// removed, or replaced, then observers that are listening to [changes]
/// will be notified.
class ObservableMap<K, V> extends Observable implements Map<K, V> {
+ /*
+ * Adapts [source] to be a `Map<K2, V2>`.
+ *
+ * Any time the set would produce a key or value that is not a [K2] or [V2],
+ * the access will throw.
+ *
+ * Any time [K2] key or [V2] value is attempted added into the adapted map,
+ * the store will throw unless the key is also an instance of [K] and
+ * the value is also an instance of [V].
+ *
+ * If all accessed entries of [source] are have [K2] keys and [V2] values
+ * and if all entries added to the returned map have [K] keys and [V]] values,
+ * then the returned map can be used as a `Map<K2, V2>`.
+ */
+
+ /// Adapts [source] to be a `ObservableMap<K2, V2>`.
+ ///
+ /// Any time the map would produce a key or value that is not a [K2] or [V2]
+ /// the access will throw.
+ ///
+ /// Any time [K2] key or [V2] value is attempted added into the adapted map,
+ /// the store will throw unless the key is also an instance of [K] and the
+ /// value is also an instance of [V].
+ ///
+ /// If all accessed entries of [source] have [K2] keys and [V2] values and if
+ /// all entries added to the returned map have [K] keys and [V] values, then
+ /// the returned map can be used as a `Map<K2, V2>`.
+ static ObservableMap<K2, V2> castFrom<K, V, K2, V2>(
+ ObservableMap<K, V> source,
+ ) {
+ return new ObservableMap<K2, V2>.spy(source._map.cast<K2, V2>());
+ }
+
final Map<K, V> _map;
/// Creates an observable map.
@@ -159,12 +192,12 @@
if (this is ObservableMap<K2, V2>) {
return this as ObservableMap<K2, V2>;
}
- return new ObservableMap.createFromType(_map.cast<K2, V2>());
+ return ObservableMap.castFrom<K, V, K2, V2>(this);
}
@override
ObservableMap<K2, V2> retype<K2, V2>() {
- return new ObservableMap.createFromType(_map.retype<K2, V2>());
+ return ObservableMap.castFrom<K, V, K2, V2>(this);
}
@override
diff --git a/pubspec.yaml b/pubspec.yaml
index 4f1b31d..0a67bfc 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
name: observable
-version: 0.21.3
+version: 0.22.0
author: Dart Team <misc@dartlang.org>
description: Support for marking objects as observable
homepage: https://github.com/dart-lang/observable
