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- import { Observable } from '../Observable';
- import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
- import { Subscription } from '../Subscription';
- import { innerFrom } from '../observable/innerFrom';
- import { createOperatorSubscriber } from './OperatorSubscriber';
- import { operate } from '../util/lift';
- export function catchError<T, O extends ObservableInput<any>>(
- selector: (err: any, caught: Observable<T>) => O
- ): OperatorFunction<T, T | ObservedValueOf<O>>;
- /**
- * Catches errors on the observable to be handled by returning a new observable or throwing an error.
- *
- * <span class="informal">
- * It only listens to the error channel and ignores notifications.
- * Handles errors from the source observable, and maps them to a new observable.
- * The error may also be rethrown, or a new error can be thrown to emit an error from the result.
- * </span>
- *
- * 
- *
- * This operator handles errors, but forwards along all other events to the resulting observable.
- * If the source observable terminates with an error, it will map that error to a new observable,
- * subscribe to it, and forward all of its events to the resulting observable.
- *
- * ## Examples
- *
- * Continue with a different Observable when there's an error
- *
- * ```ts
- * import { of, map, catchError } from 'rxjs';
- *
- * of(1, 2, 3, 4, 5)
- * .pipe(
- * map(n => {
- * if (n === 4) {
- * throw 'four!';
- * }
- * return n;
- * }),
- * catchError(err => of('I', 'II', 'III', 'IV', 'V'))
- * )
- * .subscribe(x => console.log(x));
- * // 1, 2, 3, I, II, III, IV, V
- * ```
- *
- * Retry the caught source Observable again in case of error, similar to `retry()` operator
- *
- * ```ts
- * import { of, map, catchError, take } from 'rxjs';
- *
- * of(1, 2, 3, 4, 5)
- * .pipe(
- * map(n => {
- * if (n === 4) {
- * throw 'four!';
- * }
- * return n;
- * }),
- * catchError((err, caught) => caught),
- * take(30)
- * )
- * .subscribe(x => console.log(x));
- * // 1, 2, 3, 1, 2, 3, ...
- * ```
- *
- * Throw a new error when the source Observable throws an error
- *
- * ```ts
- * import { of, map, catchError } from 'rxjs';
- *
- * of(1, 2, 3, 4, 5)
- * .pipe(
- * map(n => {
- * if (n === 4) {
- * throw 'four!';
- * }
- * return n;
- * }),
- * catchError(err => {
- * throw 'error in source. Details: ' + err;
- * })
- * )
- * .subscribe({
- * next: x => console.log(x),
- * error: err => console.log(err)
- * });
- * // 1, 2, 3, error in source. Details: four!
- * ```
- *
- * @see {@link onErrorResumeNext}
- * @see {@link repeat}
- * @see {@link repeatWhen}
- * @see {@link retry }
- * @see {@link retryWhen}
- *
- * @param selector A function that takes as arguments `err`, which is the error, and `caught`, which
- * is the source observable, in case you'd like to "retry" that observable by returning it again.
- * Whatever observable is returned by the `selector` will be used to continue the observable chain.
- * @return A function that returns an Observable that originates from either
- * the source or the Observable returned by the `selector` function.
- */
- export function catchError<T, O extends ObservableInput<any>>(
- selector: (err: any, caught: Observable<T>) => O
- ): OperatorFunction<T, T | ObservedValueOf<O>> {
- return operate((source, subscriber) => {
- let innerSub: Subscription | null = null;
- let syncUnsub = false;
- let handledResult: Observable<ObservedValueOf<O>>;
- innerSub = source.subscribe(
- createOperatorSubscriber(subscriber, undefined, undefined, (err) => {
- handledResult = innerFrom(selector(err, catchError(selector)(source)));
- if (innerSub) {
- innerSub.unsubscribe();
- innerSub = null;
- handledResult.subscribe(subscriber);
- } else {
- // We don't have an innerSub yet, that means the error was synchronous
- // because the subscribe call hasn't returned yet.
- syncUnsub = true;
- }
- })
- );
- if (syncUnsub) {
- // We have a synchronous error, we need to make sure to
- // finalize right away. This ensures that callbacks in the `finalize` operator are called
- // at the right time, and that finalization occurs at the expected
- // time between the source error and the subscription to the
- // next observable.
- innerSub.unsubscribe();
- innerSub = null;
- handledResult!.subscribe(subscriber);
- }
- });
- }
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