angular2-observables

I am having some troubles making nested Observable calls. By that I mean a call to a http service that retrieve a user, then getting the id from the user to make another http call, and finally render the results on screen. 1) HTTP GET 1 : get the User 2) HTTP GET 2: get the User's preferences passing a unique identifier as a parameter This translates into the following code in component Blah.ts : version 1 - this code does not display anything ngOnInit() { this.userService.getUser() .flatMap(u => { this.user = u; // save the user return Observable.of(u); // pass on the Observable }) .flatMap(u

Let's say I have a component that subscribes to a service function: export class Component { ... ngOnInit() { this.service.doStuff().subscribe( (data: IData) => { doThings(data); }, (error: Error) => console.error(error) ); }; }; The subscribe call takes two anonymous functions as parameters, I've managed to set up a working unit test for the data function but Karma won't accept coverage for the error one. I've tried spying on the console.error function, throwing an error and then expecting the spy to have been called but that doesn't quite do it. My unit test: spyOn(console,'error').and

In my angular 2 app I have a service that uses the Observable class from the rxjs library. import { Observable } from 'rxjs'; At the moment I am just using Observable so that I can use the toPromise() function. I read in another StackOverflow question somewhere that importing in this way and also importing from rxjs/Rx will import a whole lot of unnecessary stuff from the rxjs library that will increase the page load times and/or the code base. My question is, what is the best way to import Observable so I can use the toPromise() function without having to import everything else? Rxjs v 6.* It

I've been looking to understand those 3: Subject , Behavior subject and Replay subject . I would like to use them and know when and why, what are the benefits of using them and although I've read the documentation, watched tutorials and searched google I've failed to make any sense of this. So what are their purpose? A real-world case would be most appreciated it does not have to even code. I would prefer a clean explanation not just "a+b => c you are subscribed to ...." Thank you It really comes down to behavior and semantics. With a Subject - a subscriber will only get published values that