In Angular 2 using rxjs I was trying to convert a Promise to Observable. As many of online guides showed I used fromPromise
on Observable
. Which throws error:
Property 'fromPromise' does not exist on type 'typeof Observable'.
Observable was imported like:
import { Observable } from "rxjs/Observable";
trying to import fromPromise
like other operators results in error:
import 'rxjs/add/operator/fromPromise';
even if I suppress typescript error it still results in error:
(<any>Observable).fromPromise
Error:
Uncaught (in promise): TypeError: __WEBPACK_IMPORTED_MODULE_3_rxjs_Observable__.Observable.fromPromise is not a function
Somewhat similar issue was reported on rxjs repo here but there is no solution there either.
fromPromise(promise) Ⓢ Converts a Promises/A+ spec compliant Promise and/or ES2015 compliant Promise or a factory function which returns said Promise to an Observable sequence.
from converts various other objects and data types into Observables. It also converts a Promise, an array-like, or an iterable object into an Observable that emits the items in that promise, array, or iterable. A String, in this context, is treated as an array of characters.
UPDATE:
As of rxjs
6.0.0-beta.3, operators and observable creators should be imported from rxjs
. Furthermore, fromPromise
is not part of the public API anymore and its wrapped in the from
method.
TL;DR;
UPDATE
For rxjs 6.0.0 use:
import { from } from 'rxjs'; var observableFromPromise = from(promiseSrc);
UPDATE:
After the release of the pipeable operators in rxjs
5.5.x, the monkey patch approach is strongly discouraged. Consider to use the static method option.
Original answer
As of rxjs
5.4.x, fromPromise
can be used as a static method or can be patched into the Observable
prototype.
For the first, you can do the following:
import { fromPromise } from 'rxjs/observable/fromPromise'; var observableFromPromise = fromPromise(promiseSrc);
More info about this approach here
To do the second, you need to change your import statement:
import { Observable } from 'rxjs/Observable'; import 'rxjs/add/observable/fromPromise'; var observableFromPromise = Observable.fromPromise(promiseSrc);
More info about this approach here
Personally I would recommend the first one, considering that the 2nd approach is basically the 1rst, with the difference that the Observable
prototype is changed.
like what Jota said 'from' is the answer.
you can find the reference from here
https://www.learnrxjs.io/operators/creation/from.html
However, if you want to specify 'Promise to Observable' you could use 'fromPromise' like below.
import { from as fromPromise, Observable} from 'rxjs'; ... private getObservable(): Observable<any> { return fromPromise(this.promise); } private getPromise() { this.promise = new Promise((resolve, reject) => { this.service.getPromise() .then(response => { // do sth resolve(response); }); }); }
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With