Ember.js property initialization explanation

Question

I'm just getting started with Ember and come across this issue while writing some jasmine tests. Given I have the following code ``` App.RecipeController = Ember.Controller.extend selectedGrain: null amount: null recipeGrains: Ember.A() totalWeight: (-> weight = 0 @get('recipeGrains').forEach (grain) -> weight += grain.get('weight') weight ).property('recipeGrains.@each') addGrain: -> grain = Ember.Object.create name: @get('selectedGrain').get('name') weight: parseFloat(@get('amount')) @get('recipeGrains').pushObject(grain) @set('selectedGrain', null) @set('amount', null) ``` And I write the following test. ``` describe("Controllers", function() { describe("NewRecipeController", function() { var controller; beforeEach(function() { controller = Brewery.NewRecipeController.create(); }); it("calculates the correct total weight", function() { var grains = controller.get('recipeGrains'); grains.pushObject(Ember.Object.create({weight: 4.0})); grains.pushObject(Ember.Object.create({weight: 3…

Accepted Answer

The reason why your test fails is the default value initialization @ line 4.

You should either set the initial value in `init` method in `App.RecipeController` or passing the value at instance creation:

```
App.RecipeController = Ember.Controller.extend
  init: ->
    @set 'recipeGrains', Ember.A()
```

or

```
controller = Brewery.NewRecipeController.create({ recipeGrains: Ember.A() });
```

You should have a look to section 6 of this article.

Ember.js property initialization explanation

Solution

Problem