AngularJS コントローラーはどのようにして相互に効果的に通信できるのでしょうか?

function FirstController(someDataService) {
  // Access the data service, bind its data to the template, or interact with it to initiate server requests.
}

function SecondController(someDataService) {
  // With access to the same service instance, this controller can monitor service state updates and react accordingly.
}

function FirstController($scope) {
  // Listen for the 'someEvent' event to capture arguments and perform actions.
  $scope.$on('someEvent', function(event, args) {});
}

function SecondController($scope) {
  // Trigger the 'someEvent' event and pass any necessary arguments.
  $scope.$emit('someEvent', args);
}