Small readme tweak + added assert.

README.md

@@ -4,7 +4,7 @@ Provides an intuitive layout mechanism for [Ember.js](http://emberjs.com). The c
 
 ### How It Works
 
-The `{{dynamicView}}` binds itself to the `content` property of its containg view. When the content property is set to a subclass of `Ember.View`, the dynamic view helper's contents will be replaced with the specified view. To use a different property, simply specify it as follows: `{{dynamicView propertyName}}`.
+The `{{dynamicView}}` binds itself to the `content` property of its containg view. When the content property is set to a subclass of `Ember.View`, the dynamic view helper's contents will be replaced to reflect the new view. This property can be changed at any time. To use a different property, simply specify it as follows: `{{dynamicView propertyName}}`.
 
 ### Example Layout
 

packages/ember-layout/lib/helpers/dynamic_view.js

@@ -36,6 +36,7 @@ Ember.Handlebars.FrameView = Ember.ContainerView.extend({
   contentDidUpdate: function() {
     var blockContainer = this.get('blockContainer');
     var view = blockContainer.getPath(get(this, 'childPath'));
+    ember_assert(view instanceof Ember.View, "dynamicView's content must be set to a subclass of Ember.View'");
     var childViews = this.get('_childViews');
     var len = childViews.get('length');
     var views = view ? [view] : [];