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Triggering custom events in backbone.js

I am trying to better structure my events in backbone. Currently I have one view communicating with another by triggering events within a function, and listening for events in another function, like:
//childView
triggerFilterChange: function(e){
Backbone.trigger('filterChange',activeFilters);
}
//parentView
initialize: function(){
Backbone.on('filterChange', this.onFilterChange, this);
},
onFilterChange:function(filters){
//DO STUFF
}
This works, however, I would like to make it more clear in my child view what events should be expected, rather than just triggering something from a random function somewhere buried within the view. For example, all of my click events for the child view are clearly delineated at the top of the page:
define([
'jquery',
'underscore',
'backbone',
], function($, _, Backbone){
var ProductsFiltersView = Backbone.View.extend({
events : {
"click .filter-options-container" : "filterOptionContainerClick",
"click .filter-option" : "filterOptionClick",
},
So my question is, is there a way to put custom events into this events object? Or some structure similar to this, so you know at the top of the view what events might be triggered? Like:
events : {
"click .filter-options-container" : "filterOptionContainerClick",
"click .filter-option" : "filterOptionClick",
"filterChange" : "doFilterChange"
},
doFilterChange: function(){
Backbone.trigger('parentFilterChange',activeFilters);
}

I wouldn't touch the events object for this anyhow.
The event object defines the events from child elements of el that are propagated to the parent element (el).
The question is more about how you glue different views together.
I use intermediary custom objects (which I call controllers, as Backbone does not provide Controllers out of the box) that are used to instantiate the views and listen to events that were triggered from within the view.
You can use specified event aggregators to use within particular 'controller' objects to handle the events.
MyApp = {};
MyApp.some_vent = _.extend({}, Backbone.Events);
MyApp.some_vent.on("some:event", function(){
alert("some event was fired!");
});
If the controller holds a reference to the view where you want to cause some effect, you can execute these view's methods accordingly.

No, it is not possible.
The event hash is parsed and event handlers are set by Backbone.View.prototype.delegateEvents.
delegateEvents uses selectors and method names from events, to bind delegated jQuery (or compatible library, like Zepto) event listeners on the view's DOM element:
if (selector === '') {
this.$el.on(eventName, method);
} else {
this.$el.on(eventName, selector, method);
}
Therefore you cannot use Backbone.View.prototype.event to listen to non-DOM events (or, indeed, DOM events from outside the view's element), without overriding Backbone.View.prototype.delegateEvents with your own implementation.
As an aside, your example code is flawed - triggering filterChange would result in an infinite loop.

backbone nested collections in model listening for add

I have a model that has collections within it. Within my web app I have a project model, and in that I have an attribute called "collaborators" this attribute is actually a collection of users.
In the initialize of my view I have the following,
this.model.get('collaborators').on( 'change', alert("!!"), this);
When the view firsts loads I get an alert, firther into the view I have an event, that fires the following,
var newModel = new app.User({ id: this.clickedElement.data('userId') });
console.log(this.model.get(this.formSection)); // shows that the collection has 4 models
newModel.fetch({
success: function() {
that.model.get(that.formSection).add(newModel);
console.log(that.model.get(that.formSection)); //shows that the collection has 5 models
}
});
As you can see in the code above, I am logging my collaborators collection and it shows a length of 4, after the fetch in the success method, am I adding the model I just fetched to that collection, and then logging the collection again, this time it returns a length of 5.
This to me means that the add is successful, so is the event listener for "add" not firing after the initial page view?

The trouble is that you should pass some function as a second argument of on method. But you're firing alert right at the event binding moment and passing alert's result instead of function.
This should work correctly:
this.model.get('collaborators').on('change', function(){
alert("!!");
});
Update: But you should clarify which events you want to catch. You can find all events fired during fetching (or any other process) by launching search for trigger method calls across backbone.js file.
Update: Also you can use this code to catch all of events fired:
collaborators.on('all', function(){
/**
* `arguments` object contains all of arguments passed to the function.
* #see http://backbonejs.org/#Events-on for more details about `all`
* catching.
*/
console.log(arguments);
});

When you binding to the collaborators' change event, you should use Backbone's listenTo event.
this.listenTo(this.model.get('collaborators'), "change", function(){alert("!!"), this);
http://backbonejs.org/#Events-listenTo
The advantage of using this.listenTo is when the view gets closed/removed, Backbone will automatically invoke this.stopListening causing your view to automatically unbind the event. This will help you clean up events and prevent phantom views.
http://backbonejs.org/#Events-stopListening

What is the value and how is the model parameter being used?

Analyzing this code I am not sure what is actually happening.I keep falling into this trap with JS especially with callbacks. Here is an example taken from backbone's documentation.
//creates a new constructor function with a promptColor function as an attribute.
var Sidebar = Backbone.Model.extend({
promptColor: function() {
var cssColor = prompt("Please enter a CSS color:");
this.set({color: cssColor});
}
});
// creates a property on the global window object called sidebar
window.sidebar = new Sidebar;
// .on is an event listener and passed a callback function taking the parameters of model and color. Here is my confusion, what does it do with the model parameter?
sidebar.on('change:color', function(model, color) {
$('#sidebar').css({background: color});
});
sidebar.set({color: 'white'});
sidebar.promptColor();
My main question is what does it do with the model parameter? What is it actually doing with the model parameter?
Thanks!

In your particular case the model parameter is of no real use since their is a 1-to-1 relationship between the change event and the model.
However, there are times when this is not the case. For example, imagine you have a backbone collection of models. You can attach a "change" event listener to the collection which will get called every time any model in the collection changes. In cases like this, it's helpful to know which model originated the "change" event.

Backbone.js binding a change event to a collection inside a model

I'm pretty new to Backbone so excuse me if this question is a little obvious.
I am having problems with a collection inside of a model. When the collection changes it doesn't register as a change in the model (and doesn't save).
I have set up my model like so:
var Article = Backbone.Model.extend({
defaults: {
"emsID" : $('html').attr('id')
},
initialize: function() {
this.tags = new App.Collections.Tags();
},
url: '/editorial_dev.php/api/1/article/persist.json'
});
This works fine if I update the tags collection and manually save the model:
this.model.tags.add({p : "a"});
this.model.save();
But if the model is not saved the view doesn't notice the change. Can anyone see what I am doing wrong?

initialize: function() {
this.tags = new App.Collections.Tags();
var model = this;
this.tags.bind("change", function() {
model.save();
});
},
Bind to the change event on the inner collection and just manually call .save on your outer model.

This is actually an addendum to #Raynos answer, but it's long enough that I need answer-formatting instead of comment-formatting.
Clearly OP wants to bind to change and add here, but other people may want to bind to destroy as well. There may be other events (I'm not 100% familiar with all of them yet), so binding to all would cover all your bases.
remove also works instead of destroy. Note that both remove and destroy fire when a model is deleted--first destroy, then remove. This propagates up to the collection and reverses order: remove first, then destroy. E.g.
model event : destroy
model event : remove
collection event : destroy
collection event : remove
There's a gotcha with custom event handlers described in this blog post.
Summary: Model-level events should propagate up to their collection, but can be prevented if something handles the event first and calls event.stopPropagation. If the event handler returns false, this is a jQuery shortcut for event.stopPropagation();
event.preventDefault();
Calling this.bind in a model or collection refers to Underscore.js's bind, NOT jQuery/Zepto's. What's the difference? The biggest one I noticed is that you cannot specify multiple events in a single string with space-separation. E.g.
this.bind('event1 event2 ...', ...)
This code looks for the event called event1 event2 .... In jQuery, this would bind the callback to event1, event2, ... If you want to bind a function to multiple events, bind it to all or call bind once for each event. There is an issue filed on github for this, so this one will hopefully change. For now (11/17/2011), be wary of this.

Backbone: Why are events syntax quite different between model and view?

define events in Backbone.Model
var Todo = Backbone.Model.extend({
initialize: function(){
this.on('change', function(){
console.log('- Values for this model have changed.');
});
}
})
define events in Backbone.View
var TodoView = Backbone.View.extend({
className: "document-row",
events: {
"click .icon": "open",
"click .button.delete": "destroy"
}
})
My Question
define events syntax are quite different between model/collection and view, why are they designed in that way?
I think it's better to define model event like this. But backbone don't support it.
var Todo = Backbone.Model.extend({
events: {
"change": "foo"
},
foo: function(){
console.log("test")
}
});

There are two separate type of events: Backbone.Events and jQuery DOM events - so making these look the same seems like a bad idea as it would make code confusing not to mention it wouldn't actually work because the View UI events need different info: '<eventName> <optional DOM selector>: <methodName>' whereas normal internal events have a different syntax.
Backbone.Events follows the typical "publish/subscribe" pattern - it's just a way for apps to internally say "Something has happened" via .trigger and "I want to know when something happens" via .on or .once and the equivalent which you would use in a View because it handles cleaning up the listen when the view is removed: .listenTo and .listenToOnce.
So in your example the "change" event in the model is an internal event which Backbone fires when an attribute changes. The "change" in the View is jQuery DOM event (actually a delegate event) and you could optionally listen to something deeper in the view "change .myinput" so they are not equivalent.
The other difference is that .trigger can pass any arguments it likes after the first one (the event name), whereas the View event passes the DOM event object which you don't control e.g. onChange: function(ev) { ev.preventDefault(); }.