Optional dependencies in AngularJS

Question

I'm trying to implement a controller in AngularJS which is used across multiple pages. It makes use of some services. Some of them are loaded on all pages, some - not. I mean it is defined in different files, and these files are loaded independently. But if I do not load these services on all pages I got error:

Error: Unknown provider: firstOtionalServiceProvider <- firstOtionalService 

So, I need to load scripts on all pages. Can I declare dependency as optional in Angular? E.g:

myApp.controller('MyController', ['$scope', 'firstRequiredService', 'secondRequiredService', 'optional:firstOptionalService', 'optional:secondOptionalService', function($scope, firstRequiredService, secondRequiredService, firstOptionalService, secondOptionalSerivce){      // No need to check, as firstRequiredService must not be null     firstRequiredService.alwaysDefined();      // If the dependency is not resolved i want Angular to set null as argument and check     if (firstOptionalService) {         firstOptionalService.mayBeUndefinedSoCheckNull();     }  }]); 

Answer 1

Apparently not using automatic injection. However, you can inject the injector and check for the service:

myApp.controller('MyController', [     '$scope', '$injector', 'firstRequiredService', 'secondRequiredService',      function ($scope, $injector, firstRequiredService, secondRequiredService) {         if ($injector.has('firstOptionalService')) {             var firstOptionalService = $injector.get('firstOptionalService');         }     } ]);