Live updates for children automatically change container views.

Since traitlets does not trigger events when list elements are changed, these changes are triggered only when the entire children element is reassigned.

IPython/html/static/notebook/js/widgets/base.js

@@ -186,9 +186,30 function(widget_manager, underscore, backbone){
             // if the view name is not given, it defaults to the model's default view attribute
             var child_model = this.comm_manager.comms[comm_id].model;
             var child_view = this.widget_manager.create_view(child_model, view_name, this.cell);
-            this.child_views.push(child_view);
+            this.child_views[comm_id] = child_view;
             return child_view;
         },
+        
+        update_child_views: function(old_list, new_list) {
+            // this function takes an old list and new list of comm ids
+            // views in child_views that correspond to deleted ids are deleted
+            // views corresponding to added ids are added child_views
+        
+            // delete old views
+            _.each(_.difference(old_list, new_list), function(element, index, list) {
+                var view = this.child_views[element];
+                delete this.child_views[element];
+                view.remove();
+            }, this);
+            
+            // add new views
+            _.each(_.difference(new_list, old_list), function(element, index, list) {
+                // this function adds the view to the child_views dictionary
+                this.child_view(element);
+            }, this);
+        },
+
+        
 
         render: function(){
             // render the view.  By default, this is only called the first time the view is created

IPython/html/static/notebook/js/widgets/container.js

@@ -52,12 +52,20 define(["notebook/js/widgets/base"], function(widget_manager) {
         render: function(){
             this.$el
                 .addClass('widget-container');
-	    var children = this.model.get('children');
-	    for(var i in children) {
-		var view = this.child_view(children[i]);
-		this.$el.append(view.$el);
-	    }
-	    this.update()
+            this.children={};
+            this.update_children([], this.model.get('children'));
+            this.model.on('change:children', function(model, value, options) {
+                this.update_children(model.previous('children'), value);
+            }, this);
+            this.update()
+        },
+        
+        update_children: function(old_list, new_list) {
+            this.$el.empty();
+            this.update_child_views(old_list, new_list);
+            _.each(new_list, function(element, index, list) {
+                this.$el.append(this.child_views[element].$el);
+            }, this)
         },
         
         update: function(){

IPython/html/static/notebook/js/widgets/multicontainer.js

@@ -26,11 +26,24 define(["notebook/js/widgets/base"], function(widget_manager){
                 .attr('id', guid)
                 .addClass('accordion');
             this.containers = [];
-	    for (var i in children) {
-		this.add_child_view(this.child_view(children[i]))
-	    }
-
+            this.update_children([], this.model.get('children'));
+            this.model.on('change:children', function(model, value, options) {
+                    this.update_children(model.previous('children'), value);
+                }, this);
         },
+        
+        update_children: function(old_list, new_list) {
+            _.each(this.containers, function(element, index, list) {
+                element.remove();
+            }, this);
+            this.containers = [];
+            this.update_child_views(old_list, new_list);
+            _.each(new_list, function(element, index, list) {
+                this.add_child_view(this.child_views[element]);
+            }, this)
+        },
+        
+
         update: function() {
             // Set tab titles
             var titles = this.model.get('_titles');