crafting (and) JavaScript

How Ember methods become computed properties

At this point in the EmberJS Framework Basics Part 2 video the author explains how you can make (computed) properties out of 'normal' methods by using what the ember.js Ember.Object offers. It starts out with friend.age(), which returns what you expect. The author wants to write this as a property (as one accesses it in ember!) like this friend.get('age'). How is that done? Well, ember extends the native prototype of Function, so you can write this inside an ember object definition age: function (){}.property().

The uber magic starts when you make the age depend on the birthday. Which is done like this age: function (){}.property('birthday'). This is necessary because the computed property age is only calculated at object creation time, not on every read. In order to make it recalculate every time the birthday changes you need to observe it, as seen above.

You better learn your ember!