fieldWrapper.js

(function() {
  angular.module('myApp.directives')
    .directive('validateClass', [function() {
      return {
          restrict: 'A',
          link: function validateClassLink(scope, element, attributes, ngForm) {
              var fieldObj    = ngForm[attributes.validateClass],
                  className   = attributes.errorClass || 'has-error';
  
              scope.$watch(function() {
                  return (fieldObj.$invalid && fieldObj.$dirty);
              }, function(conditionMet) {
                  element.toggleClass(className, conditionMet);
              });
          },
          require: '^form'
      };
  }]);
}());