ref.directive.js

class RefController {
  constructor($element, $scope, $parse, $attrs){
    'ngInject';
    const tagName = $attrs.refOf || $attrs.$normalize($element[0].tagName.toLowerCase());
    let instance = $element.controller(tagName);
    if (!instance && !$attrs.refOf) {
        instance = $element;
    }
    $parse($attrs.ref).assign($scope, instance);
  }
}
function refDirective() {
  return {
    restrict: 'A',
    controller: RefController
  };
}