Example of observers in Ember

observer example.js

App = Ember.Application.create()

Person = Ember.Object.extend({
  fullName: Ember.computed(function() {
    var firstName = this.get('firstName');
    var lastName = this.get('lastName');

    return firstName + ' ' + lastName;
  }).property('firstName', 'lastName')
});

App.person = Person.create({
  firstName: "Yehuda",
  lastName: "Katz"
});

App.otherPerson = Person.create({
  firstName: "James",
  lastName: "Croft",
  iAmObserving: function(){
    // This method will be triggered when App.person firstName changes
    alert('the name was changed')
  }.observes('App.person.firstName')
});

App.person.set('firstName', "Brohuda"); // observer will fire

I had to look at that for a minute or two before I spotted line 23, which is a slightly different use to the one in the docs. The mental leap that I'd failed to make was that you could define your callback on the object that is doing the observing and specify a property relative to App, rather than on the object that contains the observed property.

Cheers for taking the time to write it up.