What is DI used for?

Question

Angular

What's the difference between

.controller('someCtrl', function($scope,mainService) {
mainService.method().....
})

and

.controller('someCtrl', function($scope) {
var myInjector = angular.injector(['app']);
 var service = myInjector.get('mainService');
service.method()...
})

Answer 1

In what can be obtained through the injector service of another application
UPD: You can request the service through $injector from the line