chore($rootScope): provide support to execute a function after the digest cycle is complete

Author: matsko

src/ng/rootScope.js

@@ -119,6 +119,7 @@ function $RootScopeProvider(){
       this['this'] = this.$root =  this;
       this.$$destroyed = false;
       this.$$asyncQueue = [];
+      this.$$postDigestQueue = [];
       this.$$listeners = {};
       this.$$isolateBindings = {};
     }
@@ -133,6 +134,7 @@ function $RootScopeProvider(){
 
 
     Scope.prototype = {
+      constructor: Scope,
       /**
        * @ngdoc function
        * @name ng.$rootScope.Scope#$new
@@ -167,6 +169,7 @@ function $RootScopeProvider(){
           child.$root = this.$root;
           // ensure that there is just one async queue per $rootScope and it's children
           child.$$asyncQueue = this.$$asyncQueue;
+          child.$$postDigestQueue = this.$$postDigestQueue;
         } else {
           Child = function() {}; // should be anonymous; This is so that when the minifier munges
             // the name it does not become random set of chars. These will then show up as class
@@ -494,6 +497,7 @@ function $RootScopeProvider(){
         var watch, value, last,
             watchers,
             asyncQueue = this.$$asyncQueue,
+            postDigestQueue = this.$$postDigestQueue,
             length,
             dirty, ttl = TTL,
             next, current, target = this,
@@ -566,6 +570,14 @@ function $RootScopeProvider(){
         } while (dirty || asyncQueue.length);
 
         clearPhase();
+
+        while(postDigestQueue.length) {
+          try {
+            postDigestQueue.shift()();
+          } catch (e) {
+            $exceptionHandler(e);
+          }
+        }
       },
 
 
@@ -696,6 +708,10 @@ function $RootScopeProvider(){
         this.$$asyncQueue.push(expr);
       },
 
+      $$postDigest : function(expr) {
+        this.$$postDigestQueue.push(expr);
+      },
+
       /**
        * @ngdoc function
        * @name ng.$rootScope.Scope#$apply

test/ng/rootScopeSpec.js

@@ -12,6 +12,12 @@ describe('Scope', function() {
     }));
 
 
+    it('should expose the constructor', inject(function($rootScope) {
+      if (msie) return;
+      expect($rootScope.__proto__).toBe($rootScope.constructor.prototype);
+    }));
+
+
     it('should not have $root on children, but should inherit', inject(function($rootScope) {
       var child = $rootScope.$new();
       expect(child.$root).toEqual($rootScope);
@@ -672,6 +678,74 @@ describe('Scope', function() {
       expect(log).toEqual('parent.async;child.async;parent.$digest;child.$digest;');
     }));
 
+    it('should not run another digest for an $$postDigest call', inject(function($rootScope) {
+      var internalWatchCount = 0;
+      var externalWatchCount = 0;
+
+      $rootScope.internalCount = 0;
+      $rootScope.externalCount = 0;
+
+      $rootScope.$evalAsync(function(scope) {
+        $rootScope.internalCount++;
+      });
+
+      $rootScope.$$postDigest(function(scope) {
+        $rootScope.externalCount++;
+      });
+
+      $rootScope.$watch('internalCount', function(value) {
+        internalWatchCount = value;
+      });
+      $rootScope.$watch('externalCount', function(value) {
+        externalWatchCount = value;
+      });
+
+      $rootScope.$digest();
+
+      expect(internalWatchCount).toEqual(1);
+      expect(externalWatchCount).toEqual(0);
+    }));
+
+    it('should run a $$postDigest call on all child scopes when a parent scope is digested', inject(function($rootScope) {
+      var parent = $rootScope.$new(),
+          child = parent.$new(),
+          count = 0;
+
+      $rootScope.$$postDigest(function() {
+        count++;
+      });
+
+      parent.$$postDigest(function() {
+        count++;
+      });
+
+      child.$$postDigest(function() {
+        count++;
+      });
+
+      expect(count).toBe(0);
+      $rootScope.$digest();
+      expect(count).toBe(3);
+    }));
+
+    it('should run a $$postDigest call even if the child scope is isolated', inject(function($rootScope) {
+      var parent = $rootScope.$new(),
+          child = parent.$new(true),
+          signature = '';
+
+      parent.$$postDigest(function() {
+        signature += 'A';
+      });
+
+      child.$$postDigest(function() {
+        signature += 'B';
+      });
+
+      expect(signature).toBe('');
+      $rootScope.$digest();
+      expect(signature).toBe('AB');
+    }));
+
     it('should cause a $digest rerun', inject(function($rootScope) {
       $rootScope.log = '';
       $rootScope.value = 0;