21,190
questions
1893
votes
35
answers
852k
views
What is the difference between Promises and Observables?
What is the difference between Promise and Observable in Angular?
An example on each would be helpful in understanding both the cases. In what scenario can we use each case?
- 19k
1066
votes
28
answers
441k
views
Angular/RxJS When should I unsubscribe from `Subscription`
When should I store the Subscription instances and invoke unsubscribe() during the ngOnDestroy life cycle and when can I simply ignore them?
Saving all subscriptions introduces a lot of mess into ...
- 12.7k
1034
votes
14
answers
684k
views
What is the difference between BehaviorSubject and Observable?
I'm looking into the design patterns of RxJS, and I do not understand the difference between BehaviorSubject and Observable.
From my understanding, BehaviorSubject can contain a value that may change. ...
- 10.4k
465
votes
10
answers
333k
views
What is the difference between Subject and BehaviorSubject?
I'm not clear on the difference between a Subject and a BehaviorSubject. Is it just that a BehaviorSubject has the getValue() function?
- 10.4k
431
votes
9
answers
391k
views
Convert Promise to Observable
I am trying to wrap my head around observables. I love the way observables solve development and readability issues. As I read, benefits are immense.
Observables on HTTP and collections seem to be ...
- 5,391
369
votes
14
answers
150k
views
Is it necessary to unsubscribe from observables created by Http methods to avoid memory leaks?
Do you need to unsubscribe from Angular 2 http calls to prevent memory leak?
fetchFilm(index) {
var sub = this._http.get(`http://example.com`)
.map(result => result.json())
...
- 24.9k
354
votes
22
answers
118k
views
What is the correct way to share the result of an Angular Http network call in RxJs 5?
By using Http, we call a method that does a network call and returns an http observable:
getCustomer() {
return this.http.get('/someUrl').map(res => res.json());
}
If we take this observable ...
348
votes
19
answers
267k
views
Angular HTTP GET with TypeScript error http.get(...).map is not a function in [null]
I have a problem with HTTP in Angular.
I just want to GET a JSON list and show it in the view.
Service class
import {Injectable} from "angular2/core";
import {Hall} from "./hall";
import {Http} ...
- 4,101
345
votes
11
answers
403k
views
How to get current value of RxJS Subject or Observable?
I have an Angular 2 service:
import {Storage} from './storage';
import {Injectable} from 'angular2/core';
import {Subject} from 'rxjs/Subject';
@Injectable()
export class SessionStorage extends ...
- 16.3k
343
votes
10
answers
299k
views
Subscribe is deprecated: Use an observer instead of an error callback
When I run the linter it says:
subscribe is deprecated: Use an observer instead of an error callback
Code from this angular app:
this.userService.updateUser(data).pipe(
tap(() => {bla ...
- 8,167
271
votes
15
answers
303k
views
Return an empty Observable
The function more() is supposed to return an Observable from a get request
export class Collection {
public more = (): Observable<Response> => {
if (this.hasMore()) {
return this....
- 13.2k
270
votes
8
answers
155k
views
Subject vs BehaviorSubject vs ReplaySubject in Angular
I've been looking to understand those 3:
Subject
BehaviorSubject
ReplaySubject
I would like to use them and know when and why, what are the benefits of using them and although I've read the ...
user6015054
255
votes
6
answers
281k
views
take(1) vs first()
I found a few implementation of AuthGuards that use take(1). In my project, I used first().
Do both work the same way?
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/first';
import { ...
- 4,042
243
votes
11
answers
99k
views
'of' vs 'from' operator
Is the only difference between Observable.of and Observable.from the arguments format? Like the Function.prototype.call and Function.prototype.apply?
Observable.of(1,2,3).subscribe(() => {})
...
- 3,431
238
votes
7
answers
149k
views
Create one-time subscription
I need to create a subscription to an Observable that is immediately disposed of when it is first called.
Is there something like:
observable.subscribeOnce(func);
My use case, I am creating a ...
- 2,795