Add Weakmap – Weak from Map -> Obj, not Obj -> Map

packages/ember-metal/lib/meta.js

@@ -33,6 +33,7 @@ import EmptyObject from 'ember-metal/empty_object';
 */
 let members = {
   cache: ownMap,
+  weak: ownMap,
   watching: inheritedMap,
   mixins: inheritedMap,
   bindings: inheritedMap,
@@ -53,6 +54,7 @@ function Meta(obj, parentMeta) {
   this._deps = undefined;
   this._chainWatchers = undefined;
   this._chains = undefined;
+  this._weak = undefined;
   // used only internally
   this.source = obj;
 
@@ -148,6 +150,18 @@ Meta.prototype._getInherited = function(key) {
   }
 };
 
+Meta.prototype.getWeak = function(symbol) {
+  var weak = this.readableWeak();
+  if (weak) {
+    return weak[symbol];
+  }
+};
+
+Meta.prototype.setWeak = function(symbol, value) {
+  var weak = this.writableWeak();
+  return weak[symbol] = value;
+};
+
 Meta.prototype._findInherited = function(key, subkey) {
   let pointer = this;
   while (pointer !== undefined) {

packages/ember-metal/lib/weak_map.js

@@ -0,0 +1,39 @@
+import { GUID_KEY } from 'ember-metal/utils';
+import { meta } from 'ember-metal/meta';
+
+var id = 0;
+
+/*
+ * @private
+ * @class Ember.WeakMap
+ *
+ * Weak relationship from Map -> Key, but not Key to Map.
+ *
+ * Key must be a non null object
+ */
+export default function WeakMap() {
+  this._id = GUID_KEY + (id++);
+}
+
+/*
+ * @method get
+ * @param key {Object}
+ * @return {*} stored value
+ */
+WeakMap.prototype.get = function(obj) {
+  var map = meta(obj).readableWeak();
+  if (map) {
+    return map[this._id];
+  }
+};
+
+/*
+ * @method set
+ * @param key {Object}
+ * @param value {Any}
+ * @return {Any} stored value
+ */
+WeakMap.prototype.set = function(obj, value) {
+  meta(obj).writableWeak()[this._id] = value;
+  return this;
+};

packages/ember-metal/tests/weak_map_test.js

@@ -0,0 +1,48 @@
+import WeakMap from 'ember-metal/weak_map';
+
+QUnit.module('Ember.WeakMap');
+
+QUnit.test('has weakMap like qualities', function(assert) {
+  var map = new WeakMap();
+  var map2 = new WeakMap();
+
+  var a = {};
+  var b = {};
+  var c = {};
+
+  equal(map.get(a), undefined);
+  equal(map.get(b), undefined);
+  equal(map.get(c), undefined);
+
+  equal(map2.get(a), undefined);
+  equal(map2.get(b), undefined);
+  equal(map2.get(c), undefined);
+
+  equal(map.set(a,  1), map, 'map.set should return itself');
+  equal(map.get(a), 1);
+  equal(map.set(b,  undefined), map);
+  equal(map.set(a, 2), map);
+  equal(map.get(a), 2);
+  equal(map.set(b,  undefined), map);
+
+  equal(map2.get(a), undefined);
+  equal(map2.get(b), undefined);
+  equal(map2.get(c), undefined);
+
+  equal(map.set(c, 1), map);
+  equal(map.get(c), 1);
+  equal(map.get(a), 2);
+  equal(map.get(b), undefined);
+
+  equal(map2.set(a, 3), map2);
+  equal(map2.set(b, 4), map2);
+  equal(map2.set(c, 5), map2);
+
+  equal(map2.get(a), 3);
+  equal(map2.get(b), 4);
+  equal(map2.get(c), 5);
+
+  equal(map.get(c), 1);
+  equal(map.get(a), 2);
+  equal(map.get(b), undefined);
+});