How to get Ember.js's bindAttr to refresh? - css

Question

I am trying to create "sort by" buttons which change sorting and css-classes when clicked on using Ember.js.
The sorting part and the initial class assignments work, however, the class assignments are not refreshed when I update the dependant properties.
What am I missing?
This is in my HTML:
<script type="text/x-handlebars" data-template-name="sort-option-item">
<dd {{bindAttr class="IsActive:active IsDesc:reversed"}}
{{action sortBy on="click"}}>{{Name}}</dd>
</script>
<script type="text/x-handlebars">
{{#each option in controller.sortOptions}}
{{view App.SortOptionView controllerBinding="option"}}
{{/each}}
</script>
An this is in my Javascript:
var App = null;
$(function () {
App = Ember.Application.create();
// Define Types:
App.SortOptionCtrl = Ember.Controller.extend({
Name: null,
Predicate: null,
Controller: null,
IsActive: false,
IsDesc: false,
sortBy: function () {
if (this.Controller != null)
this.Controller.sortBy(this.Predicate);
},
Check: function () {
this.IsActive = this.Controller != null
&& this.Controller.isSortedBy(this.Predicate);
this.IsDesc = this.Controller != null
&& this.Controller.isSortedDescBy(this.Predicate);
// adding an alert(this.IsActive); here
// proves that the function is indeed called and works as expected
}
});
App.ProductsController = Ember.ArrayController.extend({
initialized: false,
content: [],
viewContent: [],
sortProperties: ['Order'],
sortAscending: true,
sortOptions: [],
initialize: function () {
if (this.initialized == true)
return;
this.initialized = true;
var ctrl = this;
this.sortOptions.pushObject(App.SortOptionCtrl.create({
Name: 'Unsorted',
Predicate: null,
Controller: ctrl,
}));
this.sortOptions.pushObject(App.SortOptionCtrl.create({
Name: 'By Name',
Predicate: 'Name',
Controller: ctrl,
}));
this.sortOptions.pushObject(App.SortOptionCtrl.create({
Name: 'By Date',
Predicate: 'Date',
Controller: ctrl,
}));
this.sortOptions.forEach(function (opt) { opt.Check(); });
},
load: function () {
this.initialize();
// ....
},
sortBy: function (predicate) {
var prevPredicate = this.sortProperties[0];
if (predicate == prevPredicate && predicate != null) {
this.sortAscending = !(this.sortAscending);
}
else {
this.sortAscending = true;
}
this.sortProperties.length = 0;
if (predicate)
this.sortProperties.pushObject(predicate);
else
this.sortProperties.pushObject('Order');
this.sortOptions.forEach(function (opt) { opt.Check(); });
},
isSortedBy: function (predicate)
{
if (predicate == null)
predicate = 'Order';
var activePredicate = this.sortProperties[0];
if (predicate == activePredicate) {
return true;
}
else {
return false;
}
},
isSortedDescBy: function (predicate) {
if (predicate == null)
predicate = 'Order';
var activePredicate = this.sortProperties[0];
if (predicate == activePredicate) {
if (this.sortAscending)
return false;
else
return true;
}
else {
return false;
}
},
});
App.SortOptionView = Ember.View.extend({
templateName: 'sort-option-item'
});
// Create Instances:
App.productsController = App.ProductsController.create({
});
App.productsController.load();
App.initialize();
});
Versions: Ember: 1.0.0-rc.2, handlebars: 1.0.0-rc.3

Answer 1

If you want your views to react to whatever happens in the controller, you should create computed properties (via fn(){}.property('dependency')). However, in order for computed properties to work properly, you need to use Ember's get() and set() property accessors.
In your code you are doing things like
this.IsActive = this.Controller != null &&
this.Controller.isSortedBy(this.Predicate);
When you should be doing something like this:
this.set('active',
this.get('controller') != null &&
this.get('controller').isSortedBy(this.get('Predicate'))
);
You might have noticed that this code is setting a value into active, but the template is listening to isActive. That property has been changed into a computed property:
isActive: function() {
return this.get('active');
}.property('active')
It will listen for changes in the active property, and whenever that happens, it will cache the new value, and notify all subscriber objects to refresh/update.
Using Ember's get and set accessors is indicated in order to properly use the observables that make this chain of events possible.
I have modified your sample applying get and set where appropriate.
You can see it in this fiddle: http://jsfiddle.net/schawaska/fRMYu/

Answer 2

After Joe's help, more reading of Ember's manual and clean up of my code, I got to this sorter solution:
Sort option controller:
App.SortOptionCtrl = Em.Controller.extend({
Name: null,
Predicate: null,
_isActive: false,
isActive: function () {
return this.get('_isActive');
}.property('_isActive'),
_isDesc: false,
isDesc: function () {
return this.get('_isDesc');
}.property('_isDesc'),
controller: null,
updateState: function () {
if (!this.Predicate) {
this.set('_isActive', (this.get('controller')
.get('activePredicate') == null));
this.set('_isDesc', false);
}
else {
this.set('_isActive', (this.get('controller')
.get('activePredicate') == this.Predicate));
this.set('_isDesc', (this.get('_isActive')
&& !this.get('controller').get('sortAscending')));
}
}.observes('controller.activePredicate', 'controller.sortAscending'),
sortBy: function () {
if (this.get('controller') != null) {
this.get('controller').sortBy(this.Predicate);
}
},
});
Products controller:
App.ProductsController = Ember.ArrayController.extend({
content: [],
viewContent: [],
activePredicate: null,
sortProperties: ['Order'],
sortAscending: true,
sortOptions: [],
filter: function (obj) {
return true;
},
init: function () {
this._super();
var ctrl = this;
this.sortOptions.pushObject(App.SortOptionCtrl.create({
Name: 'Unsorted',
Predicate: null,
controller: ctrl,
}));
this.sortOptions.pushObject(App.SortOptionCtrl.create({
Name: 'By Name',
Predicate: 'Name',
controller: ctrl,
}));
this.sortOptions.pushObject(App.SortOptionCtrl.create({
Name: 'By Date',
Predicate: 'Date',
controller: ctrl,
}));
this.sortOptions.forEach(function (opt) {
opt.updateState();
});
},
sortBy: function (predicate) {
var prevPredicate = this.sortProperties[0];
if (predicate == prevPredicate && predicate != null) {
this.set('sortAscending', !(this.get('sortAscending')));
}
else {
this.set('sortAscending', true);
}
this.set('activePredicate', predicate);
this.set('sortProperties.length', 0);
if (predicate)
this.get('sortProperties').pushObject(predicate);
else
this.get('sortProperties').pushObject('Order');
},
});