[AngularJS Controller Inheritance]: "this" not pointing to the child controller

childCtrl.js

+(function(angular, undefined) {
  function ScholarshipsCtrl($scope, $state, $controller, Scholarship, UtilService, SCHOLARSHIP_COLUMNS) {
    // Initialize variables
    var vm = this,
        controller,
      // Assigns this variable to
      // the data assigned by the resolve to the service
      collection = [],
      columns,
      storage,
      storageProperties;

    angular.extend(collection, Scholarship.collection);

    // Inherit BaseIndexCtrl's prototype
    controller = $controller('BaseIndexCtrl', {
        $scope: $scope,
        UtilService: UtilService
    });

    angular.extend(this, controller);
    // this.prototype = Object.create(controller.prototype);

    // Column properties
    storageProperties = {
      scope: vm,
      property: 'columns',
      value: SCHOLARSHIP_COLUMNS,
      key: 'scholarships'
    };

    // Initializes localStorage instance
    // Creates a localStorage instance, then
    // binds a localStorage property
    // with the "column variable in the controller"
    storage = UtilService.Storage(storageProperties);
    columns = storage.provide();

    // Initialize data
    vm.columns = columns;
    vm.collection = collection;
    vm.remove = remove;
    vm.callServer = callServer;

    /**
     * @description  Sends a DELETE to the server
     * @see  getPageData
     * @return void
     */
    function remove() {
      var selected = vm.getSelected();
    }

    function callServer(tableState) {
      vm.load()
      var query = {};

      if (tableState.sort.predicate) {
        query.sort = tableState.sort.reverse ? '' : '-';
        query.sort += tableState.sort.predicate;
      }

      if (tableState.search.predicateObject) {
        query.filters = {};
        angular.forEach(tableState.search.predicateObject, function(value, key) {
            this[key] = value;
        }, query.filters);
      }

      getPageData(query);
    }

    /**
     * Fetches data and replaces the current
     * @param  string query
     * @return void
     */
    function getPageData(query) {
      Scholarship
        .Query
        .all(query)
        .then(vm.applyResponse)
        .catch(vm.catchPageDataError);
    }
  }

  angular
    .module('app')
    .controller('ScholarshipsCtrl', ScholarshipsCtrl);
})(angular);

parentCtrl.js

+(function(angular, _, undefined) {

  //
  // Serves as model / base for "index" controllers
  // (for tables or listing). This eliminates redundant
  // boilerplate code.
  //
  function BaseIndexCtrl($scope, UtilService) {
    var vm = this,
        columns = [],
        collection = {},
        storageProperties = {};

    vm.applyPageData = applyPageData;
    vm.catchPageDataError = catchPageDataError;
    vm.collection = collection;
    vm.columns = columns;
    vm.isLoading = false;
    vm.getSelected = getSelected;
    vm.getPage = getPage;
    vm.getPageData = getPageData;
    vm.load = load;
    vm.onColumnChange = onColumnChange;

    /**
     * @name  applyPageData
     * @description Callback function for promises after
     * a server | ajax call
     * @see  getPageData
     * @param  {[type]} response [description]
     * @return {[type]}          [description]
     */
    function applyPageData(response) {
      vm.collection = response.data;
      vm.load(false);
    }

    /**
     * @name  catchPageDataError
     * @description  Callback function for promises
     * if a promise is not resolved
     * @return {[type]} [description]
     */
    function catchPageDataError() {
      vm.load();
    }
    /**
     * @name load
     * @description Sets the load variable
     * @return void
     */
    function load(bool) {
      vm.isLoading = bool || true;
    }

    /**
     * @description  Overrides the storage instance's
     *               value when the column settings are changed
     * @return void
     */
    function onColumnChange() {
        storage.set(vm.columns);
    }

    /**
     * @name  getPage
     * @description Runs tasks, then gets pageData.
     * @param  string dir previous|next
     * @return void
     */
    function getPage(dir) {
        vm.load();

        console.log(collection);

        params = UtilService.decodeQuery(
            vm.collection.paging[dir]
        );

        getPageData(params);
    }

    /**
     * @name getPageData
     * @description Fetches data and replaces the current
     * @param  string query
     * @return void
     */
    function getPageData(query) {
      // ScholarshipSrvc
      //       .Query
      //       .all(query)
      //       .then(function(response) {
      //           loading();
      //           applyResponse(response);
      //       })
      //       .catch(function() {
      //           loading(false);
      //       });
    }

    /**
     * @name getIDSelected
     * @description Plucks the ids of each object
     * having the isSelected property as true
     * @return {Array}
     */
    function getSelected(property) {
      property || (property = 'id');
      
      return _.chain()
        .where('isSelected')
        .pluck(property)
        .value();
    }
  }

  angular
    .module('app')
    .controller('BaseIndexCtrl', BaseIndexCtrl);
})(angular, _);