materialize
Represents all of the notifications from the source Observable as next
emissions marked with their original types within Notification
objects.
materialize<T>(): OperatorFunction<T, Notification<T>>Parameters
There are no parameters.
Returns
OperatorFunction<T, Notification<T>>: An Observable that emits
Notification objects that wrap the original emissions from the source
Observable with metadata.
Description
Wraps next, error and complete emissions in
Notification objects, emitted as next on the output Observable.
materialize returns an Observable that emits a next notification for each
next, error, or complete emission of the source Observable. When the
source Observable emits complete, the output Observable will emit next as
a Notification of type "complete", and then it will emit complete as well.
When the source Observable emits error, the output will emit next as a
Notification of type "error", and then complete.
This operator is useful for producing metadata of the source Observable, to
be consumed as next emissions. Use it in conjunction with
dematerialize.
Example
Convert a faulty Observable to an Observable of Notifications
import { of } from 'rxjs';
import { materialize, map } from 'rxjs/operators';
const letters = of('a', 'b', 13, 'd');
const upperCase = letters.pipe(map(x => x.toUpperCase()));
const materialized = upperCase.pipe(materialize());
materialized.subscribe(x => console.log(x));
// Results in the following:
// - Notification {kind: "N", value: "A", error: undefined, hasValue: true}
// - Notification {kind: "N", value: "B", error: undefined, hasValue: true}
// - Notification {kind: "E", value: undefined, error: TypeError:
// x.toUpperCase is not a function at MapSubscriber.letters.map.x
// [as project] (http://1…, hasValue: false}