app.js

Editor.ElementView = Em.View.extend({
  classNameBindings: ['isSelected'],

  isSelected: false,

  selectedElementChanged: Em.observer(function(){
    var selectedElement = Editor.selectedElementController.get('content');
    var isSelected = selectedElement == this.get('content');
    this.set('isSelected', isSelected);
  }).observes('Editor.selectedElementController.content'),

  click: function(){
    // Select this element on click
    Editor.selectedElementController.set('content', this.content);
  }

});