Edit/Add ngClass in directive

Question

I am trying to create a directive to refactor some classes manipulation.

Please take a look at this fiddle .

I want to add or edit the ng-class attribute from my track directive to avoid this dupplicated code (in the ng-classes):

<table>
  <tr ng-repeat="track in tracks"
      ng-class="{
        'track-is-stopped': trackState === 'stop',
        'track-is-playing track-is-paused': trackState === 'pause',
        'track-is-playing': trackState === 'play',
        'track-is-playing track-is-buffering': trackState === 'buffering'
      }"
      track>
      <td>{{ track.title }}</td>
  </tr>
</table>

  <div ng-class="{ 
       selected: selected,
       'track-is-stopped': trackState === 'stop',
       'track-is-playing track-is-paused': trackState === 'pause',
       'track-is-playing': trackState === 'play',
       'track-is-playing track-is-buffering': trackState === 'buffering'           
     }" 
     ng-repeat="track in tracks"
     track>{{ track.title }} 
</div>

I want to control this part in my directive:

      ng-class="{
        'track-is-stopped': trackState === 'stop',
        'track-is-playing track-is-paused': trackState === 'pause',
        'track-is-playing': trackState === 'play',
        'track-is-playing track-is-buffering': trackState === 'buffering'
      }"

How to do that? It has to work with any element and has to work with any existing ng-class attribute (so I need to extend the current attribute):

ng-class="{ selected: selected }"

Answer 1

1. Create getClass() in the directive's controller:

    // ... controller: function ($scope) { $scope.getClass = function () { return { 'track-is-stopped': $scope.trackState === 'stop', 'track-is-playing track-is-paused': $scope.trackState === 'pause', 'track-is-playing': $scope.trackState === 'play', 'track-is-playing track-is-buffering': $scope.trackState === 'buffering' }; } } 

2. Call it in the view:

    <div ng-class="getClass()"> 

3. You can also safely clean the class object from duplicate classes:

    // ... return { 'track-is-stopped': $scope.trackState === 'stop', 'track-is-paused': $scope.trackState === 'pause', 'track-is-playing': $scope.trackState === 'play', 'track-is-buffering': $scope.trackState === 'buffering' }