javascript - How to use ng-toggle and ng-class to change icon while using ng-click:predicate -

i'm using predicate sort items in data model. i've working on adding in , down arrow icons show state sort in.

example of predicate orderby in action: http://plnkr.co/edit/?p=preview

not sure how toggle values within predicate:

<button type="button"         class="btn btn-default"         ng-click="predicate = 'added_epoch'; reverse=!reverse;">         <div ng-class="recentadded == 'up' ? 'iconupbig' : 'icondownbig'"></div>         added </button> 

controller

$scope.recentadded = 'up' 

i'm not using function here, why it's bit hard me see how toggle now.

---

is there way hook , change recentadded var?
inturn change ng-class:

ng-click="predicate = 'added_epoch'; reverse=!reverse;" 

then based on predicate, toggle ng-class:

ng-class="recentadded == 'up' ? 'iconupbig' : 'icondownbig'" 

i add scope function. don't want put logic in markup it's hard see what's going on.

// accept predicate using parameter $scope.togglesort = function() {   // whatever other logic need   if ($scope.recentadded === 'up') $scope.recentadded = 'down';   else $scope.recentadded = 'up'; };