es6/operators/onErrorResumeNext.js

import { FromObservable } from '../observable/FromObservable';
import { isArray } from '../util/isArray';
import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
/* tslint:enable:max-line-length */
/**
 * When any of the provided Observable emits an complete or error notification, it immediately subscribes to the next one
 * that was passed.
 *
 * <span class="informal">Execute series of Observables no matter what, even if it means swallowing errors.</span>
 *
 * <img src="./img/onErrorResumeNext.png" width="100%">
 *
 * `onErrorResumeNext` is an operator that accepts a series of Observables, provided either directly as
 * arguments or as an array. If no single Observable is provided, returned Observable will simply behave the same
 * as the source.
 *
 * `onErrorResumeNext` returns an Observable that starts by subscribing and re-emitting values from the source Observable.
 * When its stream of values ends - no matter if Observable completed or emitted an error - `onErrorResumeNext`
 * will subscribe to the first Observable that was passed as an argument to the method. It will start re-emitting
 * its values as well and - again - when that stream ends, `onErrorResumeNext` will proceed to subscribing yet another
 * Observable in provided series, no matter if previous Observable completed or ended with an error. This will
 * be happening until there is no more Observables left in the series, at which point returned Observable will
 * complete - even if the last subscribed stream ended with an error.
 *
 * `onErrorResumeNext` can be therefore thought of as version of {@link concat} operator, which is more permissive
 * when it comes to the errors emitted by its input Observables. While `concat` subscribes to the next Observable
 * in series only if previous one successfully completed, `onErrorResumeNext` subscribes even if it ended with
 * an error.
 *
 * Note that you do not get any access to errors emitted by the Observables. In particular do not
 * expect these errors to appear in error callback passed to {@link subscribe}. If you want to take
 * specific actions based on what error was emitted by an Observable, you should try out {@link catch} instead.
 *
 *
 * @example <caption>Subscribe to the next Observable after map fails</caption>
 * Rx.Observable.of(1, 2, 3, 0)
 *   .map(x => {
 *       if (x === 0) { throw Error(); }
         return 10 / x;
 *   })
 *   .onErrorResumeNext(Rx.Observable.of(1, 2, 3))
 *   .subscribe(
 *     val => console.log(val),
 *     err => console.log(err),          // Will never be called.
 *     () => console.log('that\'s it!')
 *   );
 *
 * // Logs:
 * // 10
 * // 5
 * // 3.3333333333333335
 * // 1
 * // 2
 * // 3
 * // "that's it!"
 *
 * @see {@link concat}
 * @see {@link catch}
 *
 * @param {...ObservableInput} observables Observables passed either directly or as an array.
 * @return {Observable} An Observable that emits values from source Observable, but - if it errors - subscribes
 * to the next passed Observable and so on, until it completes or runs out of Observables.
 * @method onErrorResumeNext
 * @owner Observable
 */
export function onErrorResumeNext(...nextSources) {
    if (nextSources.length === 1 && isArray(nextSources[0])) {
        nextSources = nextSources[0];
    }
    return (source) => source.lift(new OnErrorResumeNextOperator(nextSources));
}
/* tslint:enable:max-line-length */
export function onErrorResumeNextStatic(...nextSources) {
    let source = null;
    if (nextSources.length === 1 && isArray(nextSources[0])) {
        nextSources = nextSources[0];
    }
    source = nextSources.shift();
    return new FromObservable(source, null).lift(new OnErrorResumeNextOperator(nextSources));
}
class OnErrorResumeNextOperator {
    constructor(nextSources) {
        this.nextSources = nextSources;
    }
    call(subscriber, source) {
        return source.subscribe(new OnErrorResumeNextSubscriber(subscriber, this.nextSources));
    }
}
class OnErrorResumeNextSubscriber extends OuterSubscriber {
    constructor(destination, nextSources) {
        super(destination);
        this.destination = destination;
        this.nextSources = nextSources;
    }
    notifyError(error, innerSub) {
        this.subscribeToNextSource();
    }
    notifyComplete(innerSub) {
        this.subscribeToNextSource();
    }
    _error(err) {
        this.subscribeToNextSource();
    }
    _complete() {
        this.subscribeToNextSource();
    }
    subscribeToNextSource() {
        const next = this.nextSources.shift();
        if (next) {
            this.add(subscribeToResult(this, next));
        }
        else {
            this.destination.complete();
        }
    }
}
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