AngularJS：从控制器调用内部指令中的方法

Question

我有此指令

@am.directive 'modalTabSiteSheet', ( $rootScope,
                                     AMDataStore, Geocoder, Media ) ->
  restrict: 'E'
  replace:  true
  templateUrl: 'templates/modal/site/_sheet.html'

  controller: ( $scope ) ->
    DATASTORE_CACHE_KEY = 'modalTabSiteSheet'
    dataStore           = AMDataStore.getInstance()
    $scope.calculateDistance = ->
      dataStore.get DATASTORE_CACHE_KEY, "/sites/#{$scope.site.id}/distances", {}, (data) ->
        $scope.distances = JSON.parse(data.distances)
        console.log $scope.distances


    $scope.calculateDistance()

，我想从另一个控制器调用$ scope.calculateDistance（）：

@am.controller 'ModalSiteController', ( $scope, $uibModalInstance, $translate, $routeParams,
                                        AMDataStore, GetModal,
                                        site ) ->

  DATASTORE_CACHE_KEY = 'ModalSiteController'
  dataStore           = AMDataStore.getInstance()

  $scope.site  = site
  $scope.input =
    isEditModeEnabled: false

  unless $scope.site.radius
    dataStore.get DATASTORE_CACHE_KEY, "/settings", {}, (data) ->
      $scope.site.radius = _( data.settings() ).findWhere( key: "default_radius" ).formattedValue()

  if $scope.site.isNewRecord()
    $scope.site.company_id = $scope.currentCompany.id
    $scope.site.address_id = dataStore.addresses.add().id
    $scope.isNewRecord = true
    $scope.input.isEditModeEnabled = true

  $scope.$watch 'site', ( site ) ->
    if site
      $scope.buttonAction =
        label: $translate.instant( 'btn.save' )
        disabled: true


  $scope.$watch 'site.name', ( name ) ->
    $scope.buttonAction.enabled = name?


  **$scope.save = ->
    $scope.site.saveWithChildren()**

应该在$ scope.save操作中调用该方法，我应该使用$ rootScope还是有其他更好的方法？