title: Binding in ng-class in angularjs
body: <p>In the code below,i am having a variable in controller named "selectedDesignAreaId"
   and i bind this variable with the current value of "designarea.id",but when i change "selectedDesignAreaId" to any of the value of designAreaId in repeater the class is not
  updated...Always 'unSelectedCanvas' is setted...</p>
  
  <pre><code>&lt;div ng-repeat="designArea in productView.designAreas" style="position:absolute;left:{{designArea.x}}px ; top:{{designArea.y}}px;background-color: #ffdead"
                   ng-click="onDesignAreaClick(designArea.id)"
                   ng-class="{true: 'selectedCanvas', false:'unSelectedCanvas'}[(designArea.id == selectedDesignAreaId)]"&gt;
  </code></pre>