$http.js

let ctrl = this,
  listType = 'following',
  listItems,
  state;
  
let fetchData = ( ) => {
  state = 'pending';
  $http({
    url: `/api/user/list/${listType}`
  })
    .success( ( response ) => {
      listItems = response;
      state = 'resolved';
    })
    .error( ( response ) => {
      listItems = null;
      state = 'rejected';
    });
};

ctrl.getListItems = ( ) => listItems;
ctrl.isLoading = ( ) => state === 'pending';

ctrl.setListType = ( type ) => {
  if(listType !== type) {
    listType = type;
    fetchData();
  }
};

resource.js

let ctrl = this;
  listType = 'following',
  listResource = resource(
    ( ) => `/api/user/list/${listType}`,
    { scope: $scope }
  );
  
ctrl.getListItems = ( ) => listResource.data();
ctrl.isLoading = ( ) => listResource.state() === 'pending';

ctrl.setListType = ( type ) => {
  listType = type;
};