@reactivex/rxjs/src/operator/materialize.ts

Reactive Extensions for modern JavaScript

import {Operator} from '../Operator';
import {Observable} from '../Observable';
import {Subscriber} from '../Subscriber';
import {Notification} from '../Notification';

/**
 * Represents all of the notifications from the source Observable as `next`
 * emissions marked with their original types within {@link Notification}
 * objects.
 *
 * <span class="informal">Wraps `next`, `error` and `complete` emissions in
 * {@link Notification} objects, emitted as `next` on the output Observable.
 * </span>
 *
 * <img src="./img/materialize.png" width="100%">
 *
 * `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
 * {@link dematerialize}.
 *
 * @example <caption>Convert a faulty Observable to an Observable of Notifications</caption>
 * var letters = Rx.Observable.of('a', 'b', 13, 'd');
 * var upperCase = letters.map(x => x.toUpperCase());
 * var materialized = upperCase.materialize();
 * materialized.subscribe(x => console.log(x));
 *
 * @see {@link Notification}
 * @see {@link dematerialize}
 *
 * @return {Observable<Notification<T>>} An Observable that emits
 * {@link Notification} objects that wrap the original emissions from the source
 * Observable with metadata.
 * @method materialize
 * @owner Observable
 */
export function materialize<T>(): Observable<Notification<T>> {
  return this.lift(new MaterializeOperator());
}

export interface MaterializeSignature<T> {
  (): Observable<Notification<T>>;
}

class MaterializeOperator<T> implements Operator<T, Notification<T>> {
  call(subscriber: Subscriber<Notification<T>>, source: any): any {
    return source._subscribe(new MaterializeSubscriber(subscriber));
  }
}

/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class MaterializeSubscriber<T> extends Subscriber<T> {
  constructor(destination: Subscriber<Notification<T>>) {
    super(destination);
  }

  protected _next(value: T) {
    this.destination.next(Notification.createNext(value));
  }

  protected _error(err: any) {
    const destination = this.destination;
    destination.next(Notification.createError(err));
    destination.complete();
  }

  protected _complete() {
    const destination = this.destination;
    destination.next(Notification.createComplete());
    destination.complete();
  }
}