From 5eb968553a1130461ab8704535691e00eb154ac2 Mon Sep 17 00:00:00 2001
From: Matias Niemelä
Date: Fri, 15 Mar 2013 15:42:00 -0400
Subject: feat(Scope): add $watchCollection method for observing collections

The new method allows to shallow watch collections (Arrays/Maps).
---
 src/ng/rootScope.js | 141 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)

(limited to 'src')

diff --git a/src/ng/rootScope.js b/src/ng/rootScope.js
index 48ba038f..1fad7b0e 100644
--- a/src/ng/rootScope.js
+++ b/src/ng/rootScope.js
@@ -320,6 +320,147 @@ function $RootScopeProvider(){
         };
       },
 
+
+      /**
+       * @ngdoc function
+       * @name ng.$rootScope.Scope#$watchCollection
+       * @methodOf ng.$rootScope.Scope
+       * @function
+       *
+       * @description
+       * Shallow watches the properties of an object and fires whenever any of the properties change
+       * (for arrays this implies watching the array items, for object maps this implies watching the properties).
+       * If a change is detected the `listener` callback is fired.
+       *
+       * - The `obj` collection is observed via standard $watch operation and is examined on every call to $digest() to
+       *   see if any items have been added, removed, or moved.
+       * - The `listener` is called whenever anything within the `obj` has changed. Examples include adding new items
+       *   into the object or array, removing and moving items around.
+       *
+       *
+       * # Example
+       * <pre>
+          $scope.names = ['igor', 'matias', 'misko', 'james'];
+          $scope.dataCount = 4;
+
+          $scope.$watchCollection('names', function(newNames, oldNames) {
+            $scope.dataCount = newNames.length;
+          });
+
+          expect($scope.dataCount).toEqual(4);
+          $scope.$digest();
+
+          //still at 4 ... no changes
+          expect($scope.dataCount).toEqual(4);
+
+          $scope.names.pop();
+          $scope.$digest();
+
+          //now there's been a change
+          expect($scope.dataCount).toEqual(3);
+       * </pre>
+       *
+       *
+       * @param {string|Function(scope)} obj Evaluated as {@link guide/expression expression}. The expression value
+       *    should evaluate to an object or an array which is observed on each
+       *    {@link ng.$rootScope.Scope#$digest $digest} cycle. Any shallow change within the collection will trigger
+       *    a call to the `listener`.
+       *
+       * @param {function(newCollection, oldCollection, scope)} listener a callback function that is fired with both
+       *    the `newCollection` and `oldCollection` as parameters.
+       *    The `newCollection` object is the newly modified data obtained from the `obj` expression and the
+       *    `oldCollection` object is a copy of the former collection data.
+       *    The `scope` refers to the current scope.
+       *
+       * @returns {function()} Returns a de-registration function for this listener. When the de-registration function is executed
+       * then the internal watch operation is terminated.
+       */
+      $watchCollection: function(obj, listener) {
+        var self = this;
+        var oldValue;
+        var newValue;
+        var changeDetected = 0;
+        var objGetter = $parse(obj);
+        var internalArray = [];
+        var internalObject = {};
+        var oldLength = 0;
+
+        function $watchCollectionWatch() {
+          newValue = objGetter(self);
+          var newLength, key;
+
+          if (!isObject(newValue)) {
+            if (oldValue !== newValue) {
+              oldValue = newValue;
+              changeDetected++;
+            }
+          } else if (isArray(newValue)) {
+            if (oldValue !== internalArray) {
+              // we are transitioning from something which was not an array into array.
+              oldValue = internalArray;
+              oldLength = oldValue.length = 0;
+              changeDetected++;
+            }
+
+            newLength = newValue.length;
+
+            if (oldLength !== newLength) {
+              // if lengths do not match we need to trigger change notification
+              changeDetected++;
+              oldValue.length = oldLength = newLength;
+            }
+            // copy the items to oldValue and look for changes.
+            for (var i = 0; i < newLength; i++) {
+              if (oldValue[i] !== newValue[i]) {
+                changeDetected++;
+                oldValue[i] = newValue[i];
+              }
+            }
+          } else {
+            if (oldValue !== internalObject) {
+              // we are transitioning from something which was not an object into object.
+              oldValue = internalObject = {};
+              oldLength = 0;
+              changeDetected++;
+            }
+            // copy the items to oldValue and look for changes.
+            newLength = 0;
+            for (key in newValue) {
+              if (newValue.hasOwnProperty(key)) {
+                newLength++;
+                if (oldValue.hasOwnProperty(key)) {
+                  if (oldValue[key] !== newValue[key]) {
+                    changeDetected++;
+                    oldValue[key] = newValue[key];
+                  }
+                } else {
+                  oldLength++;
+                  oldValue[key] = newValue[key];
+                  changeDetected++;
+                }
+              }
+            }
+            if (oldLength > newLength) {
+              // we used to have more keys, need to find them and destroy them.
+              changeDetected++;
+              for(key in oldValue) {
+                if (oldValue.hasOwnProperty(key) && !newValue.hasOwnProperty(key)) {
+                  oldLength--;
+                  delete oldValue[key];
+                }
+              }
+            }
+          }
+          return changeDetected;
+        }
+
+        function $watchCollectionAction() {
+          listener(newValue, oldValue, self);
+        }
+
+        return this.$watch($watchCollectionWatch, $watchCollectionAction);
+      },
+
       /**
        * @ngdoc function
        * @name ng.$rootScope.Scope#$digest
-- 
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