switchMap is usually used when you have some async operation that is triggered by some prepended “event/stream”. The difference to e.g. flatMap or concatMap is, that as soon as the next trigger emits, the current async operation is canceled and re-triggered. In your case this means, that as soon as the route-params change, your hero-service … Read more
You are correct; switchMap will unsubscribe from the Observable returned by its project argument as soon as it has invoked the project function again to produce a new Observable. RxJs is incredibly powerful and dense, but its high level of abstraction can sometimes make code hard to understand. Let me debunk the marble diagrams and … Read more
Assume DynamicFormService.getAnswers(‘CAR00PR’) is asynchronous(probably it is), using async Pipe to pass asynchronous result is on the right way, but you cannot expect to get the asynchronous result right now when DynamicFormComponent is created(at ngOnInit) because of Asynchonous. The result isn’t ready yet when running your below line of code. this.form = this.qcs.toFormGroup(this.answers); There are several … Read more
No need to convert it. Just create a subject and attach observable to it with : obs.subscribe(sub) example: var obs = new rxjs.Observable((s) => {setTimeout(()=>{s.next([1])} , 500)}) //observable var sub = new rxjs.BehaviorSubject([0]) //create subject obs.subscribe(sub) //<—– HERE —– attach observable to subject setTimeout(() => {sub.next([2, 3])}, 1500) //subject updated sub.subscribe(a => console.log(a)) //subscribe to … Read more
return of(); doesn’t create a stream. Whereas return of(void 0); does. if you are mocking and need to return a stream of void. Like my life. [Sad Panda]
Subject In your case, you could simply use a Subject. A subject allows you to share a single execution with multiple observers when using it as a proxy for a group of subscribers and a source. In essence, here’s your example using a subject: const subject = new Subject(); function trigger(something) { subject.next(something); } subject.subscribe((x) … Read more
did you try with this import? it works for me import {Observable} from ‘rxjs/Rx’; import ‘rxjs/add/operator/map’;
Lettable instance operators should be imported from rxjs/operators: import { map } from ‘rxjs/operators’; As opposed to non-lettable equivalents which are imported from rxjs/operator: import { map } from ‘rxjs/operator/map’; To learn more about lettable operator read: RxJS: Understanding Lettable Operators
I encountered a similar problem and solved it using Aran’s suggestion to reference Cory Rylan’s Angular 2 Observable Data Services blog post. The key for me was using BehaviorSubject. Here’s the snippets of the code that ultimately worked for me. Data Service: The data service creates an internal BehaviorSubject to cache the data once when … Read more
As was pointed out by artur grzesiak in the comments, the BehaviorSubject interface was cleaned up, and the getter is now just myBehaviorSubject.value. I just wanted to add this as an answer because I almost didn’t read the comments to the original question, and would have missed the correct answer.