ember computed properties executed when

Question

I have inherited a codebase written in Ember 0.9.8.1 In some cases it can be very slow. I'm in the process of narrowing down why it is slow. I have noticed the following.

A function in an ArrayController is called to load data. To load the data it gets json from the backend (fast) and then for every row it creates an (previously defined) Ember.Object (slow) and push that to the content[] of the ArrayController.

Example:

App.ExOb = Ember.Object.extend({
  data1: null,
  data2: null,
  func1: function () { // statements }.property('data1').cacheable()
  func2: function () { // statements }.property('data2').cacheable()
..etc..
})

App.lotsOfData = Ember.ArrayController.create({
  content: [],
  loaddata: function() { 
    var self=this;
    get_data().forEach(function (row, index) {
       var d = App.ExOb.create(row.data);
       self.pushObject(d);
    }
  }
})

I'm trying to figure out why the creation and push of the Ember.Object is slow. What I did notice was that on creation of the object (in the example App.ExOb.create()) every property function of the object (in the example func1() and func2()) is called.

I've tried a small bit of ember code to see why this would happen but can't seem to emulate this. The only time I can see the computed property being executed is when I do a get() of that property.

Can anyone tell me (or point me to documentation that I missed) when a computed property function is executed (other than doing a get() ofcourse :-) )?

Edit: So far I found the following reasons to execute a computed property: 1. Calling/using the property directly 2. Using the propery in a handlebars template that is shown in the browser.

Joachim H. Skeie Joachim H. Skeie · Accepted Answer · 2012-09-26T10:17:45

This is just a quick stab at the problem, but have you tried to create the ExOb and initialize its properties manually, something like:

self.pushObject(App.ExOb.create({
    data1: row.data.data1,
    data2: row.data.data2,
    ... etc ...
});

That might be faster, as Ember doesn't have to guess at what to copy from the row.data object and into the App.ExOb object.

Generally, the func1() and func2() functions wouldn't need to be overloaded upon object creation in my mind, but your requirements might dictate otherwise.

ember computed properties executed when

1 Answers