Implement Model-Driven-Views spec for Dart

pkg/observe/lib/src/observable_map.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 observe;
+
+// TODO(jmesserly): this needs to be faster. We currently require multiple
+// lookups per key to get the old value.
+// TODO(jmesserly): this doesn't implement the precise interfaces like
+// LinkedHashMap, SplayTreeMap or HashMap. However it can use them for the
+// backing store.
+
+// TODO(jmesserly): should we summarize map changes like we do for list changes?
+class MapChangeRecord extends ChangeRecord {
+  /** The map key that changed. */
+  final key;
+
+  // TODO(jmesserly): we could store this more compactly if it matters.
+  /** True if this key was inserted. */
+  final bool isInsert;
+
+  /** True if this key was removed. */
+  final bool isRemove;
+
+  MapChangeRecord(this.key, {this.isInsert: false, this.isRemove: false}) {
+    if (isInsert && isRemove) {
+      throw new ArgumentError(
+          '$key cannot be inserted and removed in the same change');
+    }
+  }
+
+  // Use == on the key, to match equality semantics of most Maps.
+  bool changes(otherKey) => key == otherKey;
+}
+
+/**
+ * Represents an observable map of model values. If any items are added,
+ * removed, or replaced, then observers that are listening to [changes]
+ * will be notified.
+ */
+class ObservableMap<K, V> extends ObservableBase implements Map<K, V> {
+  static const _LENGTH = const Symbol('length');
+
+  final Map<K, V> _map;
+
+  /** Creates an observable map. */
+  ObservableMap() : _map = new HashMap<K, V>();
+
+  /** Creates a new observable map using a [LinkedHashMap]. */
+  ObservableMap.linked() : _map = new LinkedHashMap<K, V>();
+
+  /** Creates a new observable map using a [SplayTreeMap]. */
+  ObservableMap.sorted() : _map = new SplayTreeMap<K, V>();
+
+  /**
+   * Creates an observable map that contains all key value pairs of [other].
+   * It will attempt to use the same backing map type if the other map is a
+   * [LinkedHashMap], [SplayTreeMap], or [HashMap]. Otherwise it defaults to
+   * [HashMap].
+   *
+   * Note this will perform a shallow conversion. If you want a deep conversion
+   * you should use [toObservable].
+   */
+  factory ObservableMap.from(Map<K, V> other) {
+    var result = new ObservableMap<K, V>._createFromType(other);
+    other.forEach((K key, V value) { result[key] = value; });
+    return result;
+  }
+
+  factory ObservableMap._createFromType(Map<K, V> other) {
+    ObservableMap result;
+    if (other is SplayTreeMap) {
+      result = new ObservableMap<K, V>.sorted();
+    } else if (other is LinkedHashMap) {
+      result = new ObservableMap<K, V>.linked();
+    } else {
+      result = new ObservableMap<K, V>();
+    }
+    return result;
+  }
+
+  Iterable<K> get keys => _map.keys;
+
+  Iterable<V> get values => _map.values;
+
+  int get length =>_map.length;
+
+  bool get isEmpty => length == 0;
+
+  bool containsValue(V value) => _map.containsValue(value);
+
+  bool containsKey(K key) => _map.containsKey(key);
+
+  V operator [](K key) => _map[key];
+
+  void operator []=(K key, V value) {
+    int len = _map.length;
+    V oldValue = _map[key];
+    _map[key] = value;
+    if (hasObservers) {
+      if (len != _map.length) {
+        notifyField(_LENGTH, len, _map.length);
+        notifyChange(new MapChangeRecord(key, isInsert: true));
+      } else if (!identical(oldValue, value)) {
+        notifyChange(new MapChangeRecord(key));
+      }
+    }
+  }
+
+  V putIfAbsent(K key, V ifAbsent()) {
+    int len = _map.length;
+    V result = _map.putIfAbsent(key, ifAbsent);
+    if (hasObservers && len != _map.length) {
+      notifyField(_LENGTH, len, _map.length);
+      notifyChange(new MapChangeRecord(key, isInsert: true));
+    }
+    return result;
+  }
+
+  V remove(K key) {
+    int len = _map.length;
+    V result =  _map.remove(key);
+    if (hasObservers && len != _map.length) {
+      notifyChange(new MapChangeRecord(key, isRemove: true));
+      notifyField(_LENGTH, len, _map.length);
+    }
+    return result;
+  }
+
+  void clear() {
+    int len = _map.length;
+    if (hasObservers && len > 0) {
+      _map.forEach((key, value) {
+        notifyChange(new MapChangeRecord(key, isRemove: true));
+      });
+      notifyField(_LENGTH, len, 0);
+    }
+    _map.clear();
+  }
+
+  void forEach(void f(K key, V value)) => _map.forEach(f);
+
+  String toString() => Maps.mapToString(this);
+}