Backbone.js .on('add') to Collection is not causing a render - backbone.js

Question

I am following CodeSchool's 'Anatomy of Backbone.js' and cannot get this to work on my machine. There are similar questions, but they have a lot of extra stuff going on and, for someone brand-new like me, it's making it hard to learn.
Here's the code as simple/universal as possible:
var WorldEvent = Backbone.Model.extend({});
var WorldEventView = Backbone.View.extend({
events: {
'click' : 'focusEvent'
},
focusEvent: function(){
alert('great.');
},
className : 'pin bounce',
render : function () {
console.log('did something');
this.$el.html("rendered");
return this;
}
});
var WorldEventCollection = Backbone.Collection.extend({
model: WorldEvent,
url: '/events'
});
var worldEventCollection = new WorldEventCollection();
var worldEventCollectionView = new WorldEventView({
collection: worldEventCollection,
initialize: function(){
this.collection.on('add', this.addOne, this);
this.collection.on('reset', this.addAll, this);
},
addOne: function(myEvent){
var worldEventView = new WorldEventView({ model: myEvent });
this.$el.append(worldEventView.render().el);
},
addAll: function(){
this.collection.forEach(this.addOne, this);
},
render: function(){
this.addAll();
}
});
The good news is that if I call
worldEventCollection.add(new WorldEvent( {<my data>} ));
... the new model is added to worldEventCollection - I've logged worldEventCollection and worldEventCollection.length to verify.
The bad news is that "did something" doesn't appear in the console and I see no evidence of a render.
Please help, I've wasted a ton of time on what is probably super simple. Thank you.
UPDATE
Okay, I found one of my issues. I needed to define a separate WorldEventCollectionView class altogether, so this was NOT correct:
var worldEventCollectionView = new WorldEventView({
collection: worldEventCollection,
...
Instead, I believe one correct approach is:
var WorldEventCollectionView = Backbone.View.extend({
initialize: function(){
this.collection.on('add', this.addOne, this.collection);
...
And then:
var worldEventCollectionView = new WorldEventCollectionView({ collection: worldEventCollection });

Answer 1

WorldEventView.render must end with return this; as per backbone view convention, otherwise chaining such as worldEventView.render().el will not work. Specifically, that will throw an exception since render() returns undefined and you try to access the .el property of undefined.
There's several other things that are not quite right about your snippet as well, but fix that first and see if you can take it from there. Generally in a view's render method, you want to populate HTML inside the view's this.$el and return this; at the end of render and really that's all you should be doing. Render has a very specific purpose and code that isn't following that basic idea and semantic belongs elsewhere.
Oh so this:
var worldEventCollectionView = new WorldEventView({
should be:
var WorldEventCollectionView = Backbone.View.extend({