Ember.js nested property calculations returning undefined - ember.js

Question

I'm having an issue with two levels of calculated properties. I'm a bit new to ember so would appreciate some pointers.
The basic problem is that there are two levels of calculated properties - one at the order level and one at the item level. The order level is dependent on the calculation on the item.
After binding to the form - the item level calculation works great and the form is updated as I change the quantity. The order total however does not seem to calculate at all. Am I missing something in the property dependencies?
App.Order = DS.Model.extend({
items: DS.hasMany('item', { async: true } ),
payment_cash: DS.attr('number'),
payment_card: DS.attr('number'),
payment_credit: DS.attr('number'),
balance: DS.attr('number'),
total: function() {
return this.get('items').reduce(function(value,lineItem) {
value += lineItem.get('total');
});
}.property("items.#each.total"),
itemCount: function() {
return this.get('items').reduce(function(value,lineItem) {
value += lineItem.get('quantity');
});
}.property("items.#each.quantity"),
});
App.Item = DS.Model.extend({
order: DS.belongsTo('item'),
product: DS.belongsTo('product'),
quantity: DS.attr('number'),
adjustment: DS.attr('number'),
total: function() {
return this.get('product.price') * this.get('quantity')
}.property('product.price', 'quantity' )
});
App.Product = DS.Model.extend( {
name: DS.attr('string'),
description: DS.attr('string'),
price: DS.attr('number'),
imagePath: DS.attr('string')
});

Answer 1

The problem is that your reduce function is not returning anything. Try this:
total: function() {
return this.get('items').reduce( function(value, lineItem) {
return value += lineItem.get('total');
}, 0 );
}.property("items.#each.total"),
itemCount: function() {
return this.get('items').reduce( function(value, lineItem) {
return value += lineItem.get('quantity');
} , 0);
}.property("items.#each.quantity"),