Representing a Single Model with ObjectController Edit Page


Use Ember.ObjectController to represent a single model. To tell an ObjectController which model to represent, set its model property in your route's setupController method.

When a template asks an ObjectController for the value of a property, the controller looks for a property with the same name on itself first before checking the model.

For example, imagine you are writing a music player. You have defined your SongController to represent the currently playing song.

1
2
3
App.SongController = Ember.ObjectController.extend({
  soundVolume: 1
});

In the Song route, you set the model of the controller to the currently playing song:

1
2
3
4
5
App.SongRoute = Ember.Route.extend({
  setupController: function(controller, song) {
    controller.set('model', song);
  }
});

In your template, you want to display the name of the currently playing song, as well as the volume at which it is playing.

1
2
3
4
5
6
<p>
  <strong>Song</strong>: {{name}} by {{artist}}
</p>
<p>
  <strong>Current Volume</strong>: {{soundVolume}}
</p>

Because name and artist are persisted information, and thus stored on the model, the controller looks them up there and provides them to the template.

soundVolume, however, is specific to the current user's session, and thus stored on the controller. The controller can return its own value without consulting the model.

The advantage of this architecture is that it is easy to get started by accessing the properties of the model via the object controller. If, however, you need to transform a model property for a template, there is a well-defined place to do so without adding view-specific concerns to the model.

For example, imagine we want to display the duration of the song:

1
2
3
4
5
6
<p>
  <strong>Song</strong>: {{name}} by {{artist}}
</p>
<p>
  <strong>Duration</strong>: {{duration}}
</p>

This is saved on the server as an integer representing the number of seconds, so our first attempt looks like this:

1
2
3
4
5
6
<p>
  <strong>Song</strong>: 4 Minute Warning by Radiohead
</p>
<p>
  <strong>Duration</strong>: 257
</p>

Since our users are humans and not robots, however, we'd like to display the duration as a formatted string.

This is very easy to do by defining a computed property on the controller which transforms the model's value into a human-readable format for the template:

1
2
3
4
5
6
7
8
9
App.SongController = Ember.ObjectController.extend({
  duration: function() {
    var duration = this.get('model.duration'),
         minutes = Math.floor(duration / 60),
         seconds = duration % 60;

    return [minutes, seconds].join(':');
  }.property('model.duration')
});

Now, the output of our template is a lot friendlier:

1
2
3
4
5
6
<p>
  <strong>Song</strong>: 4 Minute Warning by Radiohead
</p>
<p>
  <strong>Duration</strong>: 4:17
</p>