Models produce events that you can listen to. This is useful when there are multiple representations of the same instance on the page. If one representation is updated, the other representation should be updated.

Events also provide a more traditional MVC approach. View-Controllers bind to a specific property. If that property changes, the View-Controller updates itself.

Model provides two ways to listen for events on model instances:

Way 1: Bind

You can bind to attribute changes in a model instance just like you would with events in jQuery.

The following listens for contact birthday changes.

contact.bind("birthday", function(ev, birthday){
  // do something
})

The 'birthday' event is triggered whenever an attribute is successfully changed:

contact.attr('birthday', "10-20-1982");

Bind is the prefered approach if you're favoring a more traditional MVC architecture. However, this can sometimes be more complex than the subscribe method because of maintaining additional event handlers.

Way 2: Subscribe

If OpenAjax.hub is available, Models also publish events when an instance is created, updated, or destroyed.

You can subscribe to these events with OpenAjax.hub like:

OpenAjax.hub.subscribe(
  "contact.updated", 
  function(called, contact){
    //do something ...
})

Typically, you'll subscribe with the jquery/controller/subscribe plugin like:

$.Controller.extend("Subscriber",{

  ...

  "todo.destroyed subscribe" : function(called, todo){

    //find the contact in this widget:
    var el = todo.elements(this.element)

    //remove element
    el.remove();
  },

  ...
})