Switching to Angular - Third Edition

Building a hierarchy of injectors

In order to gain a better understanding of the paragraph, let's take a look at this simple example:

// ch6/manual-injector/simple-example.tsclass Http { }class UserService {  constructor(public http: Http) { }}const parentInjector = Injector.create([{  provide: Http,  deps: [],  useFactory() {    return new Http();  }}]);const childInjector = Injector.create([{  provide: UserService,  deps: [Http],  useFactory(http) {    return new UserService(http);  }}], parentInjector);console.log(childInjector.get(UserService));console.log(childInjector.get(Http) === parentInjector.get(Http));

The imports are omitted since they are not essential to explaining the code. We have two services, Http and UserService, where UserService depends ...